Methods of controlling PCRAM devices in single-level-cell (SLC) and multi-level-cell (MLC) modes and a controller for performing the same methods

ABSTRACT

Various embodiments provide methods for configuring a phase-change random-access memory (PCRAM) structures, such as PCRAM operating in a single-level-cell (SLC) mode or a multi-level-cell (MLC) mode. Various embodiments may support a PCRAM structure being operating in a SLC mode for lower power and a MLC mode for lower variability. Various embodiments may support a PCRAM structure being operating in a SLC mode or a MLC mode based at least in part on an error tolerance for a neural network layer.

BACKGROUND

A phase-change random-access memory (PCM or PCRAM) is a form ofnon-volatile random-access computer memory. PCRAM technology is basedupon a material that can be either amorphous or crystalline at normalambient temperatures. During conditions in which the material is in theamorphous state, the material has a high electrical resistance. Theamorphous state can be referred to as a high resistance state (HRS).During conditions in which the material is in the crystalline state, thematerial has a low electrical resistance. The crystalline state can bereferred to as a low resistance state (LRS).

In order to control the state of the material, the material may beheated and cooled. By heating the material above its crystallizationpoint, the material enters its crystalline state. The material may beheated, for example, by passing current through a heating element. Asthe material cools, it enters an amorphous state. The change of phase ina PCRAM cell and the resulting change in electrical resistance can beused to store data in the PCRAM cell.

To change the phase of the PCRAM cell, a SET operation switches thematerial of the PCRAM cell to the crystalline phase and a RESEToperation switches the material of the PCRAM into the amorphous phase.The SET operation crystallizes the material of the PCRAM by heating itabove its crystallization temperature, and the RESET operationmelt-quenches the material of the PCRAM to make the material amorphous.The SET operation and the RESET operation can be associated withdifferent electrical current profiles or voltage profiles, such as onetype of pulses for the RESET operation that heat the material of thePCRAM above its melting temperature and another type of pulses for theSET operation to heat the material of the PCRAM above itscrystallization temperature but below its melting temperature.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of a phase-change random-access memory(PCRAM) structure including a phase-change memory cell and a fieldeffect transistor, according to various embodiments of the presentdisclosure.

FIG. 2 is a schematic view of a PCRAM structure including multiplephase-change memory cells, according to various embodiments of thepresent disclosure.

FIG. 3 is a vertical sectional view of a memory device including aphase-change memory cell and a FET, according to various embodiments ofthe present disclosure.

FIG. 4A is a block diagram of a memory circuit, according to variousembodiments of the present disclosure.

FIG. 4B is a block diagram of aspects of a simplified layer of a neuralnetwork, according to various embodiments of the present disclosure.

FIG. 4C is a block diagram of a neural network having multiple layers,according to various embodiments of the present disclosure.

FIG. 4D is a block diagram of another memory circuit, according tovarious embodiments of the present disclosure.

FIG. 4E is a block diagram of an example dot-product computationperformed using PCRAM cells operating in single-level-cell (SLC) mode,according to various embodiments of the present disclosure.

FIG. 4F is a block diagram of an example dot-product computationperformed using PCRAM cells operating in multi-level cell (MLC) mode,according to various embodiments of the present disclosure.

FIG. 5A is a process flow diagram illustrating a method for configuringa PCRAM cell, according to various embodiments of the presentdisclosure.

FIG. 5B is a process flow diagram illustrating a method for determininga type of a received configuration change command and selecting a RESETprogram condition, according to various embodiments of the presentdisclosure.

FIG. 6A is a process flow diagram illustrating a method for configuringa PCRAM cell, according to various embodiments of the presentdisclosure.

FIG. 6B is a process flow diagram illustrating a method for determininga type of a received configuration change command and selecting a RESETverification current condition, according to various embodiments of thepresent disclosure

FIG. 6C is a process flow diagram illustrating a method for configuringa PCRAM cell, according to various embodiments of the presentdisclosure.

FIG. 6D is a process flow diagram illustrating a method for determininga type of a received configuration change command and selecting a RESETverification voltage condition, according to various embodiments of thepresent disclosure.

FIG. 7A is a process flow diagram illustrating a method for configuringa PCRAM cell, according to various embodiments of the presentdisclosure.

FIG. 7B is a process flow diagram illustrating a method for programminga PCRAM cell, according to various embodiments of the presentdisclosure.

FIG. 8 is a process flow diagram illustrating a method for programming aPCRAM cell, according to various embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

Ranges can be expressed herein as from “about” one particular value,and/or to “about” another particular value. When such a range isexpressed, examples include from the one particular value and/or to theother particular value. Similarly, when values are expressed asapproximations, by use of the antecedent “about” or “substantially” itwill be understood that the particular value forms another aspect. Itwill be further understood that the endpoints of each of the ranges aresignificant both in relation to the other endpoint, and independently ofthe other endpoint.

The present disclosure is directed to semiconductor devices andoperating methods for the same, specifically including methods forcontrolling a phase-change random-access memory (PCRAM) structure tooperate in a single-level-cell (SLC) mode and/or a multi-level cell(MLC) mode. The present disclosure is also related to methods forprogramming a PCRAM structure, such as a PCRAM structure that is part ofartificial intelligence (AI) hardware, to operate in a SLC mode and/or aMLC mode based on aspects of a neural network, such an error tolerancefor a neural network layer or other attributes of the neural network.

A phase-change random-access memory (PCRAM) is a non-volatile memorydevice that leverages different resistive phases and heat induced phasetransition between the phases of phase-change materials and resistivematerials. Examples of the phase-change materials may be, but are notlimited to, chalcogenide materials, such as germanium-antimony-tellurium(GeSbTe or GST) materials (e.g., Ge₂Sb₂Te₅, GeTe—Sb₂Te₃, etc.), and/oraluminum-antimony materials (e.g., Al₅₀Sb₅₀, etc.). Other suitablechalcogenide materials are within the contemplated scope of disclosure.A PCRAM may be composed of many memory cells that operate independently.A PCRAM cell may include a heater and a resistor. The PCRAM cell mayoperate as a data storage element made mainly of a reversiblephase-change material to provide at least two dramatically differentresistivities for logical “0” state and “1” state. To read a state(data) from the PCRAM cell, a sufficiently small current is applied tothe phase-change material without triggering the heater to generateheat. In this way, the resistivity of the phase-change material may bemeasured and the states representing the resistivities, i.e., a “0”state for high resistivity or a “1” state for low resistivity can beread.

To write a state (data) in the PCRAM cell, for example, to write a “1”state representing a low resistivity phase of the phase-change material,a medium electric current may be applied to the heater which generatesheat for annealing the phase-change material at a temperature above thecrystallization temperature but below the melting temperature of thephase-change material for a time period to achieve a crystalline phase.As the phase-change material heats to a temperature above thecrystallization temperature, the material may enter a crystalline statewhere the phase-change material exhibits a low electrical resistance.With the low resistance value, a charge may flow into the material toestablish the “1” state value.

To write a “0” state representing a high resistivity phase of thephase-change material, a very large electric current may be applied tothe heater to generate heat to melt the phase-change material at atemperature higher than the melting temperature of the phase-changematerial; and the electric current is abruptly cut off to lower thetemperature to below the crystallization temperature of the phase-changematerial to quench and stabilize the amorphous structure of phase-changematerial. As the phase change material enters the amorphous state, thephase-change material exhibits a high resistance value. The highresistance value may impede a charge from flowing into the material toestablish a “0” state value. The very large electric current can thus bein a pulse form.

PCRAM cells may have the ability to achieve a number of distinctintermediary states, thereby having the ability to hold single bits in asingle cell supporting a single-level-cell (SLC) mode or multiple bitsin a single cell, such as two bits supporting a multiple-level-cell(MLC) mode. In a SLC mode, the PCRAM may sometimes be referred to as aSLC type memory structure. In a MLC mode, the PCRAM may sometimes bereferred to as a MLC type memory structure. In a SLC mode, the PCRAM mayfluctuate between a high resistance state (HRS) in response to a RESEToperation and a low resistance state (LRS) in response to a SEToperation. In a MLC mode, the PCRAM may be controlled to achieve one ofmultiple intermediate states between the HRS in response to the RESEToperation and the LRS in response to the SET operation.

While both a PCRAM cell operating in a SLC mode and a PCRAM celloperating in a MLC mode may be controlled by SET and RESET operations,the current operating mode of the PCRAM cell, such as a SLC mode or MLCmode, may have an impact on different SET program behavior depending onthe strength of the preceding RESET operation that occurred. Forexample, when a RESET state of the PCRAM cell was programmed with a highenergy, a subsequent SET transition may exhibit a generally smoothtransition, thereby favoring MLC programming. As another example, when apreceding RESET state of the PCRAM cell was programmed with a lowenergy, the subsequent SET transition may exhibit an abrupt transition,thereby favoring SLC programming. As the strength of the preceding RESEToperation that occurred may impact the SLC mode and/or MLC modeoperation, a PCRAM cell programming flow that transits between SLC modeand MLC mode without considering the impact of RESET behavior on thePCRAM cell may be a suboptimal programming flow. As an example, when apreceding RESET state of the PCRAM cell was programmed with a highenergy, subsequent SLC programming may be more power hungry as comparedto a RESET state of the PCRAM cell that was programmed with a lowenergy. As another example, when a preceding RESET state of the PCRAMcell was programmed with a low energy, subsequent MLC programming may beless controllable as compared to a RESET state of the PCRAM cell thatwas programmed with a high energy.

FIG. 1 is a schematic view of a PCRAM structure 10 constructed accordingto an embodiment. The PCRAM structure 10 may include one phase-changememory cell 100 and a current-controlling device 700 connected together.The phase-change memory cell 100 includes a phase-change material layerinterposed between two electrodes. In some embodiments, the resistanceof the phase-change layer material may be configured to be adjusted intomultiple levels that represent different logic states, respectively. Inembodiments in which a phase-change layer material is configured to beadjusted into multiple levels that represent different logic states,respectively, the PCRAM structure 10 may be considered to be operatingin a multiple-level-cell (MLC) mode. In some embodiments, the resistanceof the phase-change layer material may be configured to be adjusted to asingle level that represent a single logic state. In scenarios in whicha phase-change layer material is configured to be adjusted to a singlelevel that represent a single logic state, the PCRAM structure 10 may beconsidered to be operating in a single-level-cell (SLC) mode.

The current-controlling device 700 in the PCRAM structure 10 may be adevice that is operable to control the current flow through thephase-change memory cell 100 during the operations. In the presentembodiment, the current-controlling device 700 is a transistor (orselector transistor), such as a field effect transistor (FET). Forexample, the FET 700 may be a metal-oxide-semiconductor (MOS) FET. TheFET 700 includes source (S), drain (D) and gate (G). The source S anddrain D may be designed asymmetrically, such that a voltage drop overthe FET during a forming operation and an off-state leakage current maybe collectively optimized. The source S and drain D may separatelyformed, so that the source S and drain D may be independently tuned toachieve the asymmetric structure. More particularly, the source S anddrain D may be different from each other in term of dopingconcentration. In various embodiments, the source and drain may bedifferent in at least one of doping concentration, doping profile anddoping species.

The FET 700 may be electrically coupled with the memory cell 100. In anembodiment, one electrode of the memory cell 100 may be connected to thedrain D of the FET 700. The gate G of the FET 700 may be connected to aword line, and another electrode of the memory cell 100 may be connectedto a bit line, as discussed in detail with regard to FIG. 3 .

As illustrated in FIG. 1 , the gate (G), source (S), drain (D) and bodyof the FET 700 are labeled as G, S, D, and B, respectively. Thecorresponding voltages of the gate, source, drain and substrate duringthe operations are labeled as Vg, Vs, Vd and Vb, respectively.Furthermore, during operation, the current through the memory cell 100is labeled as Id, and the voltage applied to one electrode of memorycell 100 from the bit line is labeled as Vp.

In one embodiment, the PCRAM structure 10 may be a two terminal memorystructure, with the gate of the FET 700 operating as a first terminal,and one electrode of the memory cell 100 operating as a second terminal.The first terminal is controlled by a first voltage applied to the gateG of FET 700 from the word line, and the second terminal is controlledby a second voltage applied to the one electrode of the phase-changememory cell from the bit line. In one example, the source is grounded,and the body of the FET 700 is grounded or floating.

In another embodiment, the PCRAM structure 10 may be a three terminalmemory structure, wherein the three terminals include the gate of FET700 as a first terminal, the electrode of the memory cell 100 (theelectrode that is not directly connected with the drain of thetransistor) as a second terminal, and the source of the FET 700 as athird terminal. Particularly, during the operations of the phase-changememory cell 100, the first terminal (gate) may be controlled by a firstvoltage from the word line, the second terminal may be controlled by asecond voltage from the bit line, and the third terminal may becontrolled by a third voltage from a source line. In one example, thesource is grounded. In an alternative example, the second terminal isgrounded. The substrate (or the body) of the FET 700 may be grounded orfloating.

FIG. 2 is a schematic view of a memory structure 20 having a pluralityof phase-change memory cells 100 constructed according to variousembodiments of the present disclosure. With reference to FIGS. 1-2 , thephase-change memory cells 100 may be configured in an array coupled witha plurality of word lines 24 and a plurality of bit lines 26. In oneembodiment, the word lines 24 and the bit lines 26 may becross-configured. Furthermore, each of the phase-change memory cells 100may be operable to achieve single resistance levels and accordinglysingle bit storage (e.g., in a SLC mode) and/or multiple resistancelevels and accordingly multiple bit storage (e.g., in a MLC mode). Inthe present embodiment, source lines 28 are configured to connect to thesources of the memory cells 100, respectively. The source lines 28 maybe configured such that one source line 28 is coupled with onerespective phase-change memory cell 100. Alternatively, one source linemay be coupled with a subset of the phase-change memory cells 100 in thememory structure 20. In some embodiments, the memory structure 20 may beconfigured such that all phase-change memory cells 100 operate in a SLCmode at a given time. In some embodiments, the memory structure 20 maybe configured such that all phase-change memory cells 100 operate in aMLC mode at a given time. In some embodiments, the memory structure 20may be configured to be partitionable such that one or more phase-changememory cells 100 operate in a SLC mode and one or more phase changememory cells 100 operate in a MLC mode at a given time.

FIG. 3 is a cross sectional view of a memory device 200, according tovarious embodiments of the present disclosure. With reference to FIGS.1-3 , the memory device 200 includes one or more phase-change memorycells 100 and corresponding field effect transistors (FETs) 700,disposed on a substrate 30. The memory device 200 can include atwo-dimensional array of memory cells arranged in a one transistor-oneresistor (1T1R) configuration, i.e., a configuration in which one accesstransistor is connected to one resistive memory cell.

The substrate 30 can be a semiconductor substrate such as a commerciallyavailable silicon substrate. Alternatively, or additionally, thesubstrate 30 may include elementary semiconductor materials, compoundsemiconductor materials, and/or alloy semiconductor materials. Examplesof the elementary semiconductor materials may be, but are not limitedto, crystal silicon, polycrystalline silicon, amorphous silicon,germanium, and/or diamond. Examples of the compound semiconductormaterials may be, but are not limited to, silicon carbide, galliumarsenic, gallium phosphide, indium phosphide, indium arsenide, and/orindium antimonide. Examples of the alloy semiconductor materials may be,but are not limited to, SiGe, GaAsP, AlInAs, AlGaAs, GaInAs, GaInP,and/or GaInAsP. Other suitable materials within the contemplated scopeof disclosure may also be used.

The FETs 700 may provide functions that are needed to operate the memorycells 100. Specifically, the FETs 700 can be configured to control theprogramming operation, the erase operation, and the sensing (read)operation of the memory cells 100. In some embodiments, the memorydevice 200 may include sensing circuitry and/or a top electrode biascircuitry on the substrate 30. The FETs 700 may include complementarymetal-oxide-semiconductor (CMOS) transistors. While the embodimentillustrated in FIG. 3 illustrates a CMOS transistor, other FETtransistors such as fin FET, thin-film transistors (TFT), etc. may beused as well. The substrate 30 may optionally include additionalsemiconductor devices (such as resistors, diodes, capacitors, etc.).

Shallow trench isolation structures 720 including a dielectric materialsuch as silicon oxide can be formed in an upper portion of the substrate30. Suitable doped semiconductor wells, such as p-type wells and n-typewells can be formed within each area that is laterally enclosed by acontinuous portion of the shallow trench isolation structures 720.Accordingly, the FETs 700 may be formed on the substrate 30 between theisolation structures 720, such that the FETs 700 may be electricallyisolated from one another by the isolation structures 720.

Each FET 700 may include a source region 732, a drain region 738, asemiconductor channel 735 that includes a surface portion of thesubstrate 30 extending between the source region 732 and the drainregion 738, and a gate structure 750. Each gate structure 750 caninclude a gate dielectric 752, a gate electrode 754, a gate capdielectric 758, and a dielectric gate spacer 756. A source-sidemetal-semiconductor alloy region 742 can be formed on each source region732, and a drain-side metal-semiconductor alloy region 748 can be formedon each drain region 738.

In some embodiments, the channel region 735 may be doped with a firsttype dopant, and the source region 732 and the drain region 738 may bedoped with a second type dopant, opposite to the first type. In thepresent example, the FET 700 may be an n-type FET (nFET). Accordingly,the channel region 735 may be p-type channel.

In one embodiment, the source region 732 may be formed by a first ionimplantation process, and the drain region 738 may be formed by a secondion implantation process. The second ion implantation process may bedifferent from the first ion implantation process in at least one ofdoping dose, implanting angle and dopant (doping species). In oneembodiment, the first ion implantation process includes forming a firstpatterned mask on the substrate, and applying the first ion implantationto the substrate using the first patterned mask as an implantation mask.The first patterned mask may include an opening such that a substrateregion for the source is uncovered thereby. The first patterned mask maybe a patterned photoresist layer formed by a lithography process, oralternatively, a patterned hard mask formed by lithography process andetching. Similarly, the second ion implantation process may includeforming a second patterned mask on the substrate, and applying thesecond ion implantation to the substrate using the second patterned maskas an implantation mask. The second patterned mask may include anopening such that a substrate region for the drain is uncovered thereby.The second patterned mask may be similar to the first patterned mask interms of formation and composition.

Various metal interconnect structures 680 formed in dielectric materiallayers 660 may be formed over the substrate 30 and the devices formedthereon (such as the FETs 700). The dielectric material layers caninclude, for example, a contact-level dielectric material layer 601, afirst metal-line-level dielectric material layer 610, a secondline-and-via-level dielectric material layer 620, a thirdline-and-via-level dielectric material layer 630, a fourthline-and-via-level dielectric material layer 640, and a fifthline-and-via-level dielectric material layer 650.

The metal interconnect structures 680 may be formed by performing anysuitable deposition process, such as a chemical vapor deposition (CVD)process, a physical vapor deposition (PVD) process, an atomic layerdeposition (ALD) process, a high density plasma CVD (HDPCVD) process, ametal organic CVD (MOCVD) process, an electroplating process, or aplasma enhanced CVD (PECVD) process.

The metal interconnect structures may include device contact viastructures 612 formed in the contact-level dielectric material layer 601and that contact respective component of the FETs 700, first metal lines618 formed in the first metal-line-level dielectric material layer 610,first metal via structures 622 formed in a lower portion of the secondline-and-via-level dielectric material layer 620, second metal lines 628formed in an upper portion of the second line-and-via-level dielectricmaterial layer 620, second metal via structures 632 formed in a lowerportion of the third line-and-via-level dielectric material layer 630,third metal lines 638 formed in an upper portion of the thirdline-and-via-level dielectric material layer 630, third metal viastructures 642 formed in a lower portion of the fourthline-and-via-level dielectric material layer 640, fourth metal lines 648formed in an upper portion of the fourth line-and-via-level dielectricmaterial layer 640, fourth metal via structures 652 formed in a lowerportion of the fifth line-and-via-level dielectric material layer 650,and fifth metal lines 658 formed in an upper portion of the fifthline-and-via-level dielectric material layer 650. In one embodiment, themetal interconnect structures 680 can include source lines that areconnected to a source-side power supply for an array of memory elements.The voltage provided by the source lines can be applied to the bottomelectrodes through the access transistors provided in the memory arrayregion 100.

Each of the dielectric material layers (601, 610, 620, 630, 640, 650)may include a dielectric material such as undoped silicate glass, adoped silicate glass, organosilicate glass, amorphous fluorinatedcarbon, porous variants thereof, or combinations thereof. Each of themetal interconnect structures (612, 618, 622, 628, 632, 638, 642, 648,658) may include at least one conductive material, which can be acombination of a metallic liner layer (such as a metallic nitride or ametallic carbide) and a metallic fill material. Each metallic linerlayer can include TiN, TaN, WN, TiC, TaC, and WC, and each metallic fillmaterial portion can include W, Cu, Al, Co, Ru, Mo, Ta, Ti, alloysthereof, and/or combinations thereof. Other suitable materials withinthe contemplated scope of disclosure may also be used. In oneembodiment, the first metal via structures 612 and the first metal line618 may be formed as integrated line and via structures by a dualdamascene process, the second metal via structure 622 and the secondmetal lines 628 may be formed as integrated line and via structures by adual damascene process, the third metal via structures 632 and the thirdmetal lines 638 may be formed as integrated line and via structures by adual damascene process, the fourth metal via structures 642 and thefourth metal lines 648 may be formed as integrated line and viastructures by a dual damascene process, and/or the fifth metal viastructures 652 and the fourth metal lines 648 may be formed asintegrated line and via structures by a dual damascene process.

In some embodiments, the memory cells 100 may be disposed within thefifth dielectric material layer 650, and each memory cell 100 may beelectrically connected to a respective fourth metal line 648 and a fifthmetal line 658. However, the present disclosure is not limited to anyparticular location for the memory cells 100. For example, the memorycells 100 may be disposed within any of the dielectric material layers660.

The metal interconnect structures 680 may be configured to connect eachmemory cell 100 to a corresponding FET 700, and to connect the FET 700to corresponding signal lines. For example, the drain region 738 of theFET 700 may be electrically connected to a bottom electrode of thememory cell 100 via, for example, a subset of the metallic viastructures (612, 622, 632, 642) and a subset of the metal lines (618,628, 638, 648). Each drain region 738 may be connected to a first node(such as a bottom node) of a respective memory cell 100 via a respectivesubset of the metal interconnect structures 680. The gate electrode 754of each FET 700 may be electrically connected to a word line, which canbe embodied as a subset of the metal interconnect structures 680. A topelectrode of each memory cell 100 may be electrically connected to arespective bit line, which is embodied as a respective subset of themetal interconnect structures. Each source region 732 may beelectrically connected to a respective source line, which is embodied asa respective subset of the metal interconnect structures. While onlyfive levels of metal lines are illustrated in FIG. 3 , it is understoodthat more metal line levels can be formed above the illustrated levelsof FIG. 3 . Further, it is understood that the levels in which thesource lines, word lines, and bit lines are formed may be selected basedon design parameters.

FIG. 4A is a block diagram of a memory circuit 400, according to variousembodiments of the present disclosure. With reference to FIGS. 1-4A, thememory circuit 400 may be configured to implement various embodimentmethods for configuring a memory structure, such as a PCRAM cell 100 ofa PCRAM structure 10. The memory circuit 400 may be configured tocontrol an operating mode (e.g., SLC mode and/or MLC mode) of the PCRAMstructure that is part of a memory structure, such as a PCRAM cell 100of a PCRAM structure 10 that is part of a memory structure 20 having aplurality of PCRAM cells 100 and/or to control the RESET programconditions used in programming the PCRAM structure. For example, thememory circuit 400 may be configured to implement operations of methods500, 510, 600, 621, 780, 790, and/or 800 described below with referenceto FIGS. 5A-8 . Only a single structure 10 is illustrated in FIG. 4A forease of illustration, but additional structures 10 may be included inthe memory structure 20 as discussed above.

The memory circuit 400 may include a controller 401, a row decoder 402,a column selector 403, a read/write driver 404, and one or moreinput/output (I/O) buffers 405. In various embodiments, the controller401 may be coupled to the row decoder 402 and the column selector 403.In various embodiments, the row decoder 402 may be coupled to the writelines (WL), such as write lines 24 discussed above, of the memorystructure 20. The memory structure 20 may include any number of WLs 1-N,where N is an integer. The column selector 403 may be coupled to the bitlines (BL), such as bit lines 26 discussed above, of the memorystructure 20. The memory structure 20 may include any number of BLs 1-N,where N is an integer. The controller 401 may additionally be coupled tothe read/write driver 404 and/or the one or more I/O buffers 405. Theone or more I/O buffers 405 and read/write driver 404 may be coupled toone another and/or coupled to the column selector 403. The controller401 may receive various signals from external circuitry related to thecircuit 400. For example, the controller 401 may receive commands, suchas configuration change commands, from a host controller or processor totransition a PCRAM cell 100 from a SLC mode of operation to a MLC modeof operation or from a MLC mode of operation to a SLC mode of operation.The controller 401 may determine a type of a received configurationchange command to determine whether the received configuration changecommand is a SLC mode to MLC mode type configuration change command or aMLC to SLC mode type configuration change command. The controller 401may transmit signals to the row decoder 402, column selector 403, and/orread/write driver 404 to cause the row decoder 402, column selector 403,and/or read/write driver 404 to perform operations to change the statesof the PCRAM cells 100 and/or sense the states of the PCRAM cells 100.For example, the controller 401 may transmit signals to the row decoder402, column selector 403, and/or read/write driver 404 to cause the rowdecoder 402, column selector 403, and/or read/write driver 404 toperform operations to perform READ, SET, and/or RESET operations for thePCRAM cells 100 and/or to sense the current of the PCRAM cell 100 (e.g.,I_(cell)). In various embodiments, the controller 401 may selectdifferent RESET program conditions based at least in part on adetermined type of a received configuration change command. For example,a RESET program condition configured to generate a waveform with aselected current amplitude and/or pulse width may be selected inresponse to determining that a received configuration change command isa SLC mode to MLC mode type configuration change command and a differentRESET program condition configured to generate a waveform with anotherselected current amplitude and/or another pulse width may be selected inresponse to determining that a received configuration change command isa MLC mode to SLC mode type configuration change command. In variousembodiments, the controller 401 may transmit signals to the row decoder402, column selector 403, and/or read/write driver 404 to cause the rowdecoder 402, column selector 403, and/or read/write driver 404 toperform operations to program the PCRAM cell 100 using the selectedRESET program conditions.

In various embodiments, the read/write driver 404 may include a currentsensing circuit 406 and a voltage sensing circuit 407. In variousembodiments, the read/write driver 404, and/or the current sensingcircuit 406 specifically, may be configured to apply a selected readvoltage (e.g., V_(read)) to a PCRAM cell 100, and the current sensingcircuit 406 may be configured to sense the resulting cell current(I_(cell)). In various embodiments, the read/write driver 404, and/orthe current sensing circuit 406 specifically, may be configured to storethe sensed cell current (I_(cell)) in the one or more I/O buffers 405.In various embodiments, the read/write driver 404, and/or the voltagesensing circuit 407 specifically, may be configured to apply a selectedread current (e.g., I_(read)) to a PCRAM cell 100, and the voltagesensing circuit 407 may be configured to sense the resulting cellvoltage (V_(cell)). In various embodiments, the read/write driver 404,and/or the voltage sensing circuit 407 specifically, may be configuredto store the sensed cell voltage (V_(cell)) in the one or more I/Obuffers 405.

In various embodiments, the one or more I/O buffers 405 may be one ormore buffers providing storage for current sensing and/or voltagesensing results of the memory structure 20, such as I_(cell), V_(cell),etc. Additionally, the one or more I/O buffers 405 may store othervalues, such as results of comparing current sensing and/or voltagesensing (e.g., I_(cell), V_(cell), etc.) to stored threshold values,threshold values themselves (e.g., verification current conditions,verification voltage conditions, etc.), RESET program conditions (e.g.,waveform attributes, such as current amplitudes, pulse widths, etc.),etc. In various embodiments, the one or more I/O buffers 405 may beconfigured to output values, such as I_(cell), V_(cell), thresholdvalues, RESET program conditions, etc., to other circuitry, such as thecontroller 401 and/or other external circuitry related to the memorycircuit 400.

Various embodiments disclosed herein provided methods for operating amemory structure, such as a PCRAM cell 100 of a PCRAM structure 10, in aSLC mode for lower power and a MLC mode for lower variability.Specifically, various embodiments may account for RESET programconditions in operating a memory structure, such as a PCRAM cell 100 ofa PCRAM structure 10, in both SLC modes and MLC modes. ConventionalRESET operations apply the same RESET program condition whether a memorystructure, such as a PCRAM cell 100 of a PCRAM structure 10, isoperating in a SLC mode or a MLC mode. In contrast to conventional RESEToperations that are the same regardless of operating mode (i.e., thesame for SLC mode and MLC mode), various embodiments provide differentRESET program conditions based on the operating mode, such as one RESETprogram condition for SLC mode and another different RESET programcondition for MLC mode. Various embodiments may provide commands toconfigure a memory structure, such as a PCRAM cell 100 of a PCRAMstructure 10, from a SLC mode to a MLC mode and/or commands to configurea memory structure, such as a PCRAM cell 100 of a PCRAM structure 10,from a MLC mode to a SLC mode. Compared to conventional RESEToperations, the various embodiment RESET operations and/or commands tomove between SLC modes and MLC modes may enable a memory structure, suchas a PCRAM cell 100 of a PCRAM structure 10, to achieve tighter MLCresistance distribution in a MLC mode and/or lower program energyconsumption in a SLC mode.

Various embodiments disclosed herein provide commands to configure amemory structure, such as a PCRAM cell 100 of a PCRAM structure 10, froma SLC mode to a MLC mode and/or commands to configure a memorystructure, such as a PCRAM cell 100 of a PCRAM structure 10, from a MLCmode to a SLC mode, may be suitable for use in controlling artificialintelligence (AI) hardware operations, such as AI hardware including oneor more PCRAM structures 10.

One example of AI hardware may include a hardware-based neural network(e.g., a hardware-based deep neural network (DNN) or any other typeartificial neural network (ANN)) in which in-memory computing may beused to implement layers of the neural network. In-memory computingapproaches may provide benefits to implementing neural networks, such asDNNs, in comparison to von Neumann computing architectures. For example,a hardware-based neural network may achieve performance and energyefficiency in comparison to a von Neumann computing architectureimplemented neural network.

A neural network implementation may often include artificial neurons. Asignal at a connection between artificial neurons in the neural networkis often a real number. The output of each artificial neuron in theneural network may be computed by a non-linear function of the sum ofthe inputs to the artificial neuron. The connections between artificialneurons may have a weight that adjusts as learning/training of theneural network to a task is performed. The weight may adjust up or downindicating an increase or decrease in a strength of a signal at theconnection between two artificial neurons. In many implementations,artificial neurons may be aggregated into layers, and a neural networkmay be configured such that different layers perform differenttransformations on the inputs those respective layers receive. Signalsin the neural network travel from a first layer of the neural network toa last layer of the neural network and may travel through a layer morethan once in some implementations. As an example, a layer (e.g., k) of aneural network may receive a number (e.g., i) of layer inputs (e.g.,X_(i)) and apply filter weights (e.g., W_(k,i)) to the layer inputs tooutput a layer output (e.g., Y_(k)) to a next layer according to thefunction Y_(k)=ΣW_(k,i)×X_(i).

FIG. 4B is a block diagram of aspects of a simplified layer 460 of aneural network, according to various embodiments of the presentdisclosure. With reference to FIGS. 1-4B, the layer 460 may beimplemented on a memory structure 20 having a plurality of PCRAM cells100 (e.g., an array of PCRAM cells 100). The inputs of the layer 460 maybe write line (WL) inputs 461, such as inputs to write lines 24discussed above. There may be any number of WL inputs 461, such as 1-ninputs, labeled X₁ to X_(n) in FIG. 4B. The weights for the layer 460may be memory data 462, such as the equivalent resistance of the PCRAMstructure 10. The bit line (BL) values, such as values of bit lines 26discussed above, and/or source line (SL) values, such as values ofsource lines 28 discussed above, illustrated as BL/SL 463 in FIG. 4B maybe provided to a sensing circuit 464, such as a sense amplifier of aread/write driver (e.g., read/write driver 404), and the sense resultmay be the output to the next layer 465.

FIG. 4C is a block diagram of an example neural network 470 havingmultiple layers 1-N, according to various embodiments of the presentdisclosure. With reference to FIGS. 1-4C, the neural network 470 mayinclude a first layer 471, a second layer 472, and any number ofadditional layers up to a Nth layer 473. Inputs to the neural network470 may pass through the layers 471 to 473 one or more times and theresulting output after the last pass through the last layer, such aslayer 473, may be the output of the neural network. As an example, eachlayer 471 to 473 may be similar to layer 460 discussed above and may beimplemented as a hardware-based layer on a memory structure 20 having aplurality of PCRAM cells 100 (e.g., an array of PCRAM cells 100).

Each layer of the neural network 470 may have its own respectiverequirements and/or may perform its own assigned task. For example, thefirst layer 471 may perform a first task and have a first errortolerance. The second layer 472 may perform a second task and have asecond error tolerance. The first task may be the same or different thanthe second task and/or the first error tolerance may be the same ordifferent than the second error tolerance. As one example, the neuralnetwork 470 may be a neural network configured for image classificationand detection and the first layer 471 may be a convolution layer with afirst error tolerance and the second layer 472 may be a fully connectedlayer with a second error tolerance more stringent (e.g., loweracceptable error rate) than the first error tolerance. While neuralnetwork 470 is a simplified representation of a neural network, neuralnetworks suitable for use with the various embodiments may be of morecomplex design and may include any neural network architecture, examplesof which may include neural network models such as CF-VGG, VGG16,ResNet50, TiGRU, etc.

When a neural network, such as neural network 470 or any other type ofneural network, is implemented in hardware, such as at least partiallyin a memory structure 20 having a plurality of PCRAM cells 100 (e.g., anarray of PCRAM cells 100), the different requirements and/or tasksassociated with different layers of the neural network may benefit fromoperating in different modes, such as one or more layer operating in aSLC mode and/or one or more layer operating in a MLC mode. As oneexample, SLC mode operations may have a higher robustness and be lessprone to error (or fault) than MLC mode operations. As another example,MLC mode operations may be more efficient than SLC mode operations suchthat MLC mode operations may be performed with fewer PCRAM cells 100,have less latency, and/or use less energy than SLC mode operations. Asdiscussed herein, the terms “error” and “fault” may be usedinterchangeably to refer to bit errors and/or bit faults of a PCRAMcell, such as a PCRAM cell 100 of a PCRAM structure 10. The potentialdifferent characteristics of SLC mode operations and MLC mode operationsmay be associated with different layers of a neural network, such asneural network 470. For example, a layer of a neural network, such asneural network 470, having an error (or fault) tolerance above athreshold (e.g., an acceptable error rate higher than a threshold errorrate) may be associated with MLC mode operations. As the error tolerancemay be relatively high (e.g., above the threshold) the error tolerancemay support MLC operation of a PCRAM cell, such as a PCRAM cell 100 of aPCRAM structure 10, and the PCRAM cell may benefit from the reducedarea, reduced latency, and reduced energy benefits provided by shiftingto (or remaining in) MLC mode operations. As another example, a layer ofa neural network, such as neural network 470, having an error (or fault)tolerance below a threshold (e.g., an acceptable error rate lower than athreshold error rate) may be associated with SLC mode operations. As theerror tolerance may be relatively low (e.g., at or below the threshold)the error tolerance may support SLC operation of a PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10, and the PCRAM cell may benefitfrom the higher robustness provided by SLC mode operations by shiftingto (or remaining in) SLC mode operations.

In some embodiments, a PCRAM cell, such as a PCRAM cell 100 of a PCRAMstructure 10, may be shifted into (or remain in) SLC mode in response todetermining that an error tolerance for a neural network layer supportsSLC mode operation for the PCRAM cell or determining that an errortolerance for the neural network layer does not support MLC modeoperation for the PCRAM cell. In some embodiments, a PCRAM cell, such asa PCRAM cell 100 of a PCRAM structure 10, may be shifted into (or remainin) MLC mode in response to determining that an error tolerance for aneural network layer supports MLC mode operation for the PCRAM cell ordetermining that an error tolerance for the neural network layer doesnot support SLC mode operation for the PCRAM cell. Shifting to (orremaining in) SLC mode may enable a neural network layer with a morestringent bit error tolerance to have better reliability than if thatneural network layer operated in MLC mode. Shifting into (or remainingin) MLC mode may enable a neural network layer with a less stringent biterror tolerance to use less area, operate faster, and/or use less energythan if that neural network layer operated in SLC mode. In variousembodiments, a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, may shift from MLC mode to SLC mode (or MLC mode to SLC mode) on alayer-by-layer basis as each subsequent layer is executed for a neuralnetwork, such as neural network 470.

FIG. 4D is a block diagram of a memory circuit 450, according to variousembodiments of the present disclosure. With reference to FIGS. 1-4D, thememory circuit 450 may be configured to implement various embodimentmethods for configuring a memory structure, such as a PCRAM cell 100 ofa PCRAM structure 10. The memory circuit 450 may be similar to memorycircuit 400 described above, and may further include a neural networkcontroller 451. The memory circuit 450 may be configured to control anoperating mode (e.g., SLC mode and/or MLC mode) of the PCRAM structurethat is part of a memory structure, such as a PCRAM cell 100 of a PCRAMstructure 10 that is part of a memory structure 20 having a plurality ofPCRAM cells 100 and/or to control the RESET program conditions used inprogramming the PCRAM structure. For example, the memory circuit 450 maybe configured to implement operations of methods 500, 510, 600, 621,780, 790, and/or 800 described below with reference to FIGS. 5A-8 . Onlya single structure 10 is illustrated in FIG. 4B for ease ofillustration, but additional structures 10 may be included in the memorystructure 20 as discussed above.

The neural network controller 451 may receive various signals fromexternal circuitry related to the circuit 450. For example, the neuralnetwork controller 451 may receive neural network layer executionindications, from a host controller or processor. A neural network layerexecution indication may be an indication that one or more computationsfor a next layer of a neural network are to be executed by the circuit450, such as by one or more PCRAM cell 100 of the circuit 450. Theneural network layer execution indication may indicate the type ofneural network layer to be executed and/or an error tolerance for theneural network layer. The neural network controller 451 may determinewhether an error tolerance for the neural network layer supports MLCmode operation and/or supports SLC mode operation. As one example, theneural network controller 451 may receive a neural network layerexecution indication indicating a type of a next layer to be executedfor a neural network.

The network controller 451 may perform operations to determine an errortolerance associated with the type of the next layer to be executed forthe neural network, such as by retrieving the value of an errortolerance from a memory and/or parsing the neural network layerexecution indication when the error tolerance is included in the neuralnetwork execution indication. The network controller 451 may performoperations to determine whether the error tolerance for the next layerto be executed for the neural network supports MLC operation for a PCRAMcell 100 and/or may perform operations to determine whether the errortolerance for the next layer to be executed for the neural networksupports SLC operation for a PCRAM cell 100. As one specific example,the determined error tolerance may be compared to a threshold for errortolerance associated with MLC mode operation, and the determined errortolerance being higher than the threshold for error tolerance associatedwith MLC mode operation may indicate the error tolerance supports MLCmode. The determined error tolerance being at or below the threshold forerror tolerance associated with MLC mode operation may indicate theerror tolerance does not support MLC mode. As another specific example,the determined error tolerance may be compared to a threshold for errortolerance associated with SLC mode operation, and the determined errortolerance being lower than the threshold for error tolerance associatedwith SLC mode operation may indicate the error tolerance supports SLCmode. The determined error tolerance being at or above the threshold forerror tolerance associated with SLC mode operation may indicate theerror tolerance does not support SLC mode.

The neural network controller 451 may track and/or determine the stateof one or more PCRAM cells 100 in the circuit 450, such as whether anyPCRAM cell 100 is in a SLC mode and/or a MLC mode. The neural networkcontroller 451 may be configured to perform operations to generateconfiguration change commands associated with one or more PCRAM cells100, such as SLC mode to MLC mode type configuration change commandsand/or MLC to SLC mode type configuration change commands. The neuralnetwork controller 451 may be configured to perform operations todetermine whether a PCRAM cell 100 is in MLC mode or SLC mode inresponse to determining error tolerance supports MLC mode and/or inresponse to determining error tolerance does not support MLC mode. Theneural network controller 451 may be configured to perform operations todetermine whether a PCRAM cell 100 is in MLC mode or SLC mode inresponse to determining error tolerance supports SLC mode and/or inresponse to determining error tolerance does not support SLC mode. Whenthe PCRAM cell 100 is in SLC mode, the neural network controller 451 maybe configured to perform operations to generate a SLC mode to MLC modetype configuration change command in response to determining errortolerance supports MLC mode and/or in response to determining errortolerance does not support SLC mode. When the PCRAM cell 100 is in MLCmode, the neural network controller 451 may be configured to take noaction in response to determining error tolerance supports MLC modeand/or in response to determining error tolerance does not support SLCmode, thereby causing the PCRAM cell 100 to remain in MLC mode. When thePCRAM cell 100 is in MLC mode, the neural network controller 451 may beconfigured to perform operations to generate a MLC mode to SLC mode typeconfiguration change command in response to determining error tolerancesupports SLC mode and/or in response to determining error tolerance doesnot support MLC mode. When the PCRAM cell 100 is in SLC mode, the neuralnetwork controller 451 may be configured to take no action in responseto determining error tolerance supports SLC mode and/or in response todetermining error tolerance does not support MLC mode, thereby causingthe PCRAM cell 100 to remain in SLC mode.

The neural network controller 451 may transmit signals, such as signalsincluding configuration change commands associated with one or morePCRAM cells 100, to the controller 401 to cause the controller 401 toperform operations to change the states of the PCRAM cells 100 and/orsense the states of the PCRAM cells 100.

While the neural network controller 451 is illustrated in FIG. 4D as aseparate component from the controller 401, the operations discussedherein as being performed by the neural network controller 451 mayalternatively be implemented by the controller 401.

FIG. 4E is a block diagram of an example dot-product computationperformed using PCRAM cells, such as PCRAM cells 100 of PCRAM structures10, operating in SLC mode, according to various embodiments of thepresent disclosure. FIG. 4F is a block diagram of an example dot-productcomputation performed using PCRAM cells, such as PCRAM cells 100 ofPCRAM structures 10, operating in MLC mode, according to variousembodiments of the present disclosure. With reference to FIGS. 1-4F, theexample SLC mode operations of FIG. 4E and the example MLC modeoperations of FIG. 4F compare the efficiency of a memory circuit 400,450 executing the same layer of a neural network in SLC mode (FIG. 4E)and in MLC mode (FIG. 4F). The example SLC mode (FIG. 4E) layercomputation may require four PCRAM structures 10 connected to four senseamplifiers 481 to execute the layer. The example MLC mode (FIG. 4F)layer computation may require two PCRAM structures 10 connected to twosense amplifiers 481 to execute the layer. As such, the MLC mode (FIG.4F) may require less PCRAM area (e.g., less PCRAM structures) than theSLC mode (FIG. 4F) to perform the same layer. As such, the MLC mode(FIG. 4F) may use fewer memory devices (e.g., less PCRAM structures 10)than the SLC mode (FIG. 4E) thereby realizing an area benefit for theMLC mode (FIG. 4F) over the SLC mode (FIG. 4E). Additionally, thenumber/size of the components in the shift and add circuitry 482 may beless in the MLC mode (FIG. 4F) than in the SLC mode (FIG. 4E), therebyrealizing a latency and/or energy benefit for the MLC mode (FIG. 4F)over the SLC mode (FIG. 4E).

FIGS. 4E and 4F illustrate that the same input on the WL 24 of (1) inthe SLC mode (FIG. 4E) and MLC mode (FIG. 4F) results in the same outputof binary value [0111] or value of “7”. The SLC mode (FIG. 4E) approachperforms the dot-product of each bit-significance separately andcombines them afterward outside the memory macro in the shift and addcircuitry 482. In the SLC mode (FIG. 4E) approach each weight (0), (1),(1), (1) is represented by its own PCRAM cell 100. The MLC mode (FIG.4F) enables the weights to be represented by multiple levels such thattwo weights together (01) are represented by a first PCRAM cell 100 andthe other two weights (11) are represented by a second PCRAM cell 100.The shift and add operations are thereby reduced from four to twooperations as well in the MLC mode (FIG. 4F).

FIG. 5A is a process flow diagram illustrating a method 500 forconfiguring a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, according to various embodiments of the present disclosure. Withreference to FIGS. 1-5A, in various embodiments, the operations ofmethod 500 may be performed by a memory circuit, such as memory circuit400, 450, including a PCRAM structure, such as PCRAM structure 10.

In block 502, the memory circuit 400, 450 may receive a configurationchange command associated with a PCRAM cell, such as a PCRAM cell 100 ofa PCRAM structure 10. Various embodiments may include commands, such asconfiguration change commands, to configure a memory structure, such asa PCRAM cell 100 of a PCRAM structure 10, between SLC and MLC modes. Insome embodiments, a host device, such as a host controller or processor,may issue a configuration change command to a memory controller, such ascontroller 401 of memory circuit 400, 450. As one example, aconfiguration change command may be a SLC mode to MLC mode typeconfiguration change command instructing the memory controller, such ascontroller 401 of memory circuit 400, 450, to transition a memorystructure, such as a PCRAM cell 100 of a PCRAM structure 10 that is partof a memory structure 20 having a plurality of PCRAM cells 100 (e.g., anarray of PCRAM cells 100), from a SLC mode to a MLC mode. As anotherexample, a configuration change command may be a MLC mode to SLC modetype configuration change command instructing the memory controller,such as controller 401 of memory circuit 400, 450, to transition amemory structure, such as a PCRAM cell 100 of a PCRAM structure 10 thatis part of a memory structure 20 having a plurality of PCRAM cells 100(e.g., an array of PCRAM cells 100), from a MLC mode to a SLC mode.

In block 504, the memory circuit 400, 450 may determine a type of thereceived configuration change command. Various embodiments may include amemory controller, such as controller 401 of memory circuit 400, 450,determining a type of a received configuration change command. Forexample, a memory controller, such as controller 401 of memory circuit400, 450, may determine whether a received configuration change commandis a SLC mode to MLC mode type configuration change command or a MLCmode to SLC mode type configuration change command.

In block 506, the memory circuit 400, 450 may select, based at least inpart on the determined type of the received configuration changecommand, a RESET program condition from a plurality of stored RESETprogram conditions. In various embodiments, a plurality of differentRESET program conditions may be associated with different types ofconfiguration change commands. For example, buffers or other storagedevices, such as I/O buffers 405, may store a plurality of differentRESET program conditions, each associated with different types ofconfiguration change commands. As a specific example, one location maystore a RESET program condition associated with a MLC mode to SLC modetype configuration change command and another location may store a RESETprogram condition associated with a SLC mode to MLC mode typeconfiguration change command. In various embodiments, the RESET programconditions may be configured such that when selected and used (e.g.,loaded, accessed, etc.), a RESET program condition causes a memorycontroller, such as controller 401 of memory circuit 400, 450, togenerate a waveform having a current amplitude of a current valueindicated by the RESET program condition and/or a pulse width indicatedby the RESET program condition.

As a specific example, the plurality of RESET program conditions may beat least two RESET program conditions, such as a first RESET programcondition configured to generate a first waveform having a first currentamplitude and a first pulse width and a second RESET program conditionconfigured to generate a second waveform having a second currentamplitude and a second pulse width. The different RESET programconditions, such as the first RESET program condition and the secondRESET program condition, may be configured to generate different waveforms, such as the first waveform and the second waveform. The differentRESET program conditions, such as the first RESET program condition andthe second RESET program condition, may each be associated with a typeof configuration change command. For example, the first RESET programcondition may be associated with a SLC mode to MLC mode typeconfiguration change command and the second RESET program condition maybe associated with a MLC mode to SLC mode type configuration changecommand.

The different wave forms, such as the first waveform and the secondwaveform, may have different current amplitude values and/or differenttime durations. As one example, the first RESET program condition may beconfigured such that the first waveform has a first current amplitudewith a higher current value than the second current amplitude of thesecond waveform generated by the second RESET program condition. In suchan example, the time durations of the first waveform and the secondwaveform may be the same or different. As a specific example, the firstRESET program condition with the higher current value may have a currentvalue in a range of 750 microamps (μA) to 1.25 milliamps (mA), such as750 μA, 750 μA to 1 mA, 1 mA, 1 mA to 1.25 mA, 1.25 mA, etc.; althoughlesser and greater currents may also be used; and the second RESETprogram condition with the lower current value may have a current valuein a range of 250 μA to 750 μA, such as 250 μA, 250 μA to 500 μA, 500μA, 500 μA to 750 μA, 750 μA, etc.; although lesser and greater currentsmay also be used. As another example, the first RESET program conditionmay be configured such that the first pulse width has a longer timeduration than the second pulse width of the second waveform generated bythe second RESET program condition. In such an example, the currentvalues of the current amplitudes of the first waveform and the secondwaveform may be the same or different. As a specific example, the firstRESET program condition with the first pulse with a longer time durationmay have a time duration in a range of 20 nanoseconds (ns) to 400 ns,such as 20 ns, 20 ns to 200 ns, 200 ns, 200 ns to 400 ns, 400 ns, etc.;although lesser and greater time durations may also be used; and thesecond RESET program condition with the second pulse with the shortertime duration may have a time duration in a range of 20 ns to 200 ns,such as 20 ns, 20 ns to 100 ns, 100 ns, 100 ns to 200 ns, 200 ns, etc.;although lesser and greater time durations may also be used. As afurther example, the first RESET program condition may be configuredsuch that the first waveform has a first current amplitude with a highercurrent value than the second current amplitude of the second waveformgenerated by the second RESET program condition and the first pulsewidth has a longer time duration than the second pulse width of thesecond waveform generated by the second RESET program condition. As aspecific example, the first RESET program condition with the highercurrent value and the longer time duration may have a current value in arange of 750 μA to 1.25 milliamps (mA), such as 750 μA, 750 μA to 1 mA,1 mA, 1 mA to 1.25 mA, 1.25 mA, etc., and a time duration in a range of20 ns to 400 ns, such as 20 ns, 20 ns to 200 ns, 200 ns, 200 ns to 400ns, 400 ns, etc.; although lesser and greater currents and/or times mayalso be used; and the second RESET program condition with the lowercurrent value and the shorter time duration may have a current value ina range of 250 μA to 750 μA, such as 250 μA, 250 μA to 500 μA, 500 μA,500 μA to 750 μA, 750 μA, etc., and a time duration in a range of 20 nsto 200 ns, such as 20 ns, 20 ns to 100 ns, 100 ns, 100 ns to 200 ns, 200ns, etc.; although lesser and greater currents may also be used.

Regardless of the configuration, in some embodiments, when comparing twoRESET program conditions, such as the first RESET program condition andthe second RESET program condition, the RESET program condition with ahigher current value for the waveform generated by that RESET programcondition may be considered to impart a stronger RESET than the otherRESET program condition with the lower current value for the waveformgenerated by that other RESET program condition. The other RESET programcondition with the lower current value for the waveform generated bythat other RESET program condition may be considered to impart a weakerRESET in comparison to the RESET program condition with the highercurrent value for its generated waveform. As a specific example, whenthe plurality of RESET program conditions is a first RESET programcondition with a higher current value for the waveform generated by thefirst RESET program condition (e.g., thereby imparting a stronger reset)and a second RESET program condition with a lower current value for thewaveform generated by the second RESET program condition (e.g., therebyimparting a weaker reset), the current values of the first RESET programcondition and the second RESET program condition may be correlated withone another such that the higher (e.g., stronger) current value is afixed current value, such as a selected number of microamps (μA) ormilliamps (mA), greater than the lower (e.g., weaker) current value. Inthis manner, a higher (e.g., stronger) current value may be determinedby adding the fixed current value to the lower (e.g., weaker) currentvalue when the lower (e.g., weaker) current value is known or the lower(e.g., weaker) current value may be determined by subtracting the fixedcurrent value from the higher (e.g., stronger) current value when thehigher (e.g., stronger) current value is known. In some embodiments, aRESET program condition, such as the first RESET program condition,having higher current value (e.g., imparting a stronger RESET) may beassociated with a SLC mode to MLC mode type configuration change commandand a RESET program condition, such as the second RESET programcondition, having lower current value (e.g., imparting a weaker RESET)may be associated with a MLC mode to SLC mode type configuration changecommand.

In block 508, the memory circuit 400, 450 may program the PCRAM cellusing the selected RESET program condition. For example, a memorycontroller, such as controller 401 of memory circuit 400, 450, may issueone or more program waveforms according to the selected RESET programcondition. As a specific example, the controller 401 of memory circuit400, 450 may transmit signals to the row decoder 402, column selector403, and/or read/write driver 404 to cause the row decoder 402, columnselector 403, and/or read/write driver 404 to generate one or moreinstances of the program waveform according to the selected RESETprogram condition, such as one or more instances of the first waveformgenerated by the first RESET program condition or one or more instancesof the second waveform generated by the second RESET program condition.

FIG. 5B is a process flow diagram illustrating a method 510 fordetermining a type of a received configuration change command andselecting a RESET program condition, according to various embodiments ofthe present disclosure. With reference to FIGS. 1-5B, in variousembodiments, the operations of method 510 may be performed by a memorycircuit, such as memory circuit 400, 450, including a PCRAM structure,such as PCRAM structure 10. The operations of method 510 may beperformed as part of a method for configuring a PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10, according to various embodimentsof the present disclosure, such as part of the operations of method 500(FIG. 5A). As a specific example, the operations of method 510 may beperformed as part of the operations of blocks 504 and 506 of method 500(FIG. 5A), such as in response to receiving a configuration changecommand associated with a PCRAM cell in block 502.

In block 512, the memory circuit 400, 450 may determine whether thereceived configuration change command is a SLC mode to MLC mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command. As an example, the type of configurationchange command may be indicated in a received configuration changecommand itself, such as in an element of the configuration changecommand, by a value of the configuration change command, etc. As anexample, the memory circuit 400, 450 may parse or otherwise read thereceived configuration change command and compare the attributes of thereceived configuration change command to stored indications of SLC modeto MLC mode type configuration change commands and MLC mode to SLC modetype configuration change commands. A match between the attributes ofthe received configuration change command and the stored indications mayindicate the type of the received configuration change command, such aswhether the received configuration change command is a SLC mode to MLCmode type configuration change command or a MLC mode to SLC mode typeconfiguration change command.

In response to determining the received configuration change command isa SLC mode to MLC mode type configuration change command, in block 514,the memory circuit 400, 450 may select a first RESET program condition.In response to determining the received configuration change command isa MLC mode to SLC mode type configuration change command, in block 516,the memory circuit 400, 450 may select a second RESET program condition.As discussed with reference to block 506 of method 500 (FIG. 5A), insome embodiments, a RESET program condition, such as the first RESETprogram condition, having higher current value (e.g., imparting astronger RESET) may be associated with a SLC mode to MLC mode typeconfiguration change command and a RESET program condition, such as thesecond RESET program condition, having lower current value (e.g.,imparting a weaker RESET) may be associated with a MLC mode to SLC modetype configuration change command. As one example, the association maybe indicated by the storage location (e.g., a location in I/O buffer405) of the RESET program conditions, with the first RESET programcondition being stored in a location associated with SLC mode to MLCmode type configuration change commands and the second RESET programcondition being stored in a location associated with MLC mode to SLCmode type configuration change commands. Based on determining the typeof the received configuration change command, the corresponding RESETprogram condition may be selected (e.g., loaded, used, etc.).

In response to selecting the first RESET program condition in block 514or selecting the second RESET program condition in block 516, the memorycircuit 400, 450 may program the PCRAM cell using the selected RESETprogram condition in block 508 of method 500 (FIG. 5A) as describedabove.

FIG. 6A is a process flow diagram illustrating a method 600 forconfiguring a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, according to various embodiments of the present disclosure. Withreference to FIGS. 1-6A, in various embodiments, the operations ofmethod 600 may be performed by a memory circuit, such as memory circuit400, 450, including a PCRAM structure, such as PCRAM structure 10. Theoperations of method 600 may be similar to the operations of methods 500(FIG. 5A) and/or 510 (FIG. 5B) described above, except that rather thangenerating a one or more instances (e.g., one of more pulses) of a fixedamplitude and pulse width (e.g., the waveform of the selected RESETprogram condition) the operations of method 600 may provide analternative approach in which a sequence of program and verifyoperations are performed using successively increasing strength (e.g.,higher current amplitude and/or longer pulse width) instances ofprogramming waveforms to program the PCRAM cell, such as a PCRAM cell100 of a PCRAM structure 10.

In blocks 502 and 504, the memory circuit 400, 450 may performoperations of like numbered blocks of method 500 (FIG. 5A) to receive aconfiguration change command associated with a PCRAM cell and determinea type of the received configuration change command as discussed above.

In block 602, the memory circuit 400, 450 may select, based at least inpart on the determined type of the received configuration changecommand, a RESET verification current condition from a plurality ofstored RESET verification current conditions. In various embodiments, aplurality of different verification current conditions may be associatedwith different types of configuration change commands. For example,buffers or other storage devices, such as I/O buffers 405, may store aplurality of different verification current conditions, each associatedwith different types of configuration change commands. As a specificexample, one location may store a RESET verification current conditionassociated with a MLC mode to SLC mode type configuration change commandand another location may store a RESET verification current conditionassociated with a SLC mode to MLC mode type configuration changecommand. In various embodiments, the RESET verification currentconditions may be cell current value thresholds (e.g., I_(TH))configured such that the PCRAM cell current (e.g., I_(cell)) may bebelow the cell current value thresholds (e.g., I_(TH)) when the PCRAMcell, such as a PCRAM cell 100 of a PCRAM structure 10, is successfullyRESET. As a specific example, a cell current value threshold (e.g.,I_(TH)) may have a current value in a range of 0.01 μA to 0.2 μA, suchas 0.01 μA, 0.01 μA to 0.1 μA, 0.1 μA, 0.1 μA to 0.2 μA, 0.2 μA, etc.;although lesser and greater currents may also be used.

As a specific example, the plurality of RESET verification currentconditions may be at least two RESET verification current conditions,such as a first RESET verification current condition and a second RESETverification current condition. The different RESET verification currentconditions, such as the first RESET verification current condition andthe second RESET verification current condition, may each be associatedwith a type of configuration change command. For example, the firstRESET verification current condition may be associated with a SLC modeto MLC mode type configuration change command and the second RESETverification current condition may be associated with a MLC mode to SLCmode type configuration change command.

The different RESET verification current conditions, such as the firstRESET verification current condition and the second RESET verificationcurrent condition, may each be different current value thresholds (e.g.,I_(TH)). The current value thresholds (e.g., I_(TH)) may be currentvalues, such as a selected number of microamps (μA) or milliamps (mA),that the cell current (e.g., I_(cell)) should be below to indicate thatthe PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure 10, wassuccessfully RESET. In some embodiments, when comparing two RESETverification current conditions, such as the first RESET verificationcurrent condition and the second RESET verification current condition,the RESET verification current condition that is the lower current valuethreshold (e.g., I_(TH)) may be considered to be associated with astronger RESET of the PCRAM cell, such as a PCRAM cell 100 of a PCRAMstructure 10, than the other RESET verification condition with thehigher current value threshold (e.g., I_(TH)). The other RESETverification current condition with the higher current value threshold(e.g., I_(TH)) may be considered to be associated with a weaker RESET ofthe PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure 10, incomparison to the RESET verification current condition with the lowercurrent value threshold (e.g., I_(TH)). In some embodiments, a RESETverification current condition, such as the first RESET verificationcurrent condition, having lower current value threshold (e.g., I_(TH))may be associated with a SLC mode to MLC mode type configuration changecommand and a RESET verification current condition, such as the secondRESET verification current condition, having higher current value (e.g.I_(TH)) may be associated with a MLC mode to SLC mode type configurationchange command.

In block 604, the memory circuit 400, 450 may program the PCRAM cellusing a RESET pulse. For example, a memory controller, such ascontroller 401 of memory circuit 400, 450, may issue an initial (ordefault) program waveform. As a specific example, the controller 401 ofmemory circuit 400, 450 may transmit signals to the row decoder 402,column selector 403, and/or read/write driver 404 to cause the rowdecoder 402, column selector 403, and/or read/write driver 404 togenerate an initial (or default) program waveform.

In block 606, the memory circuit 400, 450 may determine a PCRAM cellcurrent. For example, the controller 401 of the memory circuit 400, 450may control a current sensing circuit (e.g., current sensing circuit406) to sense the current of the PCRAM cell (e.g., I_(cell)) when aselected read voltage (e.g., V_(read)) is applied to the PCRAM cell 100.The controller 401 of the memory circuit 400, 450 may store thedetermined current (e.g., I_(cell)) in a buffer, such as I/O buffer 405.

In block 608, the memory circuit 400, 450 may determine whether thedetermined PCRAM cell current is less than the selected RESETverification current condition. For example, the controller 401 of thememory circuit 400, 450 may compare the determined current of the PCRAMcell (e.g., I_(cell)) to the current value threshold (e.g., I_(TH)) ofthe selected RESET verification current condition, such as the firstRESET verification current condition or the second RESET verificationcurrent condition, to determine whether the determined PCRAM cellcurrent (e.g., I_(cell)) is less than the selected RESET verificationcurrent condition (e.g., I_(TH)). Comparing the determined current ofthe PCRAM cell (e.g., I_(cell)) to the current value threshold (e.g.,I_(TH)) of the selected RESET verification current condition may be donein any manner, such as by subtracting the determined current of thePCRAM cell (I_(cell)) from the current value threshold (e.g., I_(TH)) ofthe selected RESET verification current condition and determining that anon-zero positive result indicates the determined PCRAM cell current(e.g., I_(cell)) is less than the selected RESET verification currentcondition (e.g., I_(TH)) and a zero or negative result indicates thedetermined PCRAM cell current (e.g., Len) is greater than the selectedRESET verification current condition (e.g., I_(TH)). Comparing thedetermined current of the PCRAM cell (e.g., I_(cell)) to the currentvalue threshold (e.g., I_(TH)) of the selected RESET verificationcurrent condition may enable the controller 401 of the memory circuit400, 450 to determine whether or not the determined PCRAM cell currentmeets the selected RESET verification current condition. The determinedPCRAM cell current (e.g., I_(cell)) being less than the selected RESETverification current condition (e.g., I_(TH)) (i.e., thatI_(cell)<I_(Th)) may indicate to the controller 401 of the memorycircuit 400, 450 that the determined PCRAM cell current (e.g., I_(cell))meets the selected RESET verification current condition (e.g., I_(TH)).The determined PCRAM cell current (e.g., I_(cell)) not being less thanthe selected RESET verification current condition (e.g., I_(TH)) (i.e.,that I_(cell)≥I_(Th)) may indicate to the controller 401 of the memorycircuit 400, 450 that the determined PCRAM cell current (e.g., I_(cell))does not meet the selected RESET verification current condition (e.g.,I_(TH)).

In response to determining that the determined PCRAM cell current (e.g.,I_(cell)) is less than the selected RESET verification current condition(e.g., I_(TH)) (i.e., that I_(cell)<I_(Th)) the memory circuit 400, 450may indicate the RESET is verified in block 613.

In response to determining that the determined PCRAM cell current (e.g.,I_(cell)) is not less than the selected RESET verification currentcondition (e.g., I_(TH)) (i.e., that I_(cell)≥I_(Th)) the memory circuit400, 450 may modify the RESET pulse in block 611. Modifying the RESETpulse may include increasing the current amplitude and/or pulse width ofthe RESET pulse used for programming in block 604. As one example, thememory circuit 400, 450 may modify the RESET pulse to have a highervalue current amplitude than the last RESET pulse used for programmingthe PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure 10. Thepulse width of the modified RESET pulse may be same or different thanthat of the last RESET pulse used for programming the PCRAM cell, suchas a PCRAM cell 100 of a PCRAM structure 10. As another example, thememory circuit 400, 450 may modify the RESET pulse to have a longer timeduration pulse width than the last RESET pulse used for programming thePCRAM cell, such as a PCRAM cell 100 of a PCRAM structure 10. Thecurrent amplitude of the modified RESET pulse may be same or differentthan that of the last RESET pulse used for programming the PCRAM cell,such as a PCRAM cell 100 of a PCRAM structure 10. As a further example,the memory circuit 400, 450 may modify the RESET pulse to have a highercurrent amplitude and a longer time duration pulse width than those ofthe last RESET pulse used for programming the PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10. In this manner, by modifying thecurrent amplitude and/or pulse width of the RESET pulse, the RESET pulsemay be sequentially changed, such as sequentially strengthened, tomodify the RESET of the PCRAM cell, such as strengthen the RESET of thePCRAM cell until the determined PCRAM cell current (e.g., I_(cell)) isbelow the selected RESET verification current condition (e.g., I_(TH))(i.e., that I_(cell)<I_(Th)).

In response to modifying the RESET pulse, the memory circuit 400, 450may program the PCRAM cell using a RESET pulse, i.e., the now modifiedRESET pulse, in block 604. For example, a memory controller, such ascontroller 401 of memory circuit 400, 450, may issue a program waveformaccording to the modified RESET pulse. As a specific example, thecontroller 401 of memory circuit 400, 450 may transmit signals to therow decoder 402, column selector 403, and/or read/write driver 404 tocause the row decoder 402, column selector 403, and/or read/write driver404 to generate a program waveform having the modified current amplitudeand/or pulse width duration as modified in block 611. As discussedabove, in response to determining that the determined PCRAM cell current(e.g., I_(cell)) is less than the selected RESET verification currentcondition (e.g., I_(TH)) (i.e., that I_(cell)<I_(Th)) the memory circuit400, 450 may indicate the RESET is verified in block 613 (i.e., theselected RESET verification current condition (e.g., I_(TH)) is met) andin response to determining that the determined PCRAM cell current (e.g.,I_(cell)) is not less than the selected RESET verification currentcondition (e.g., I_(TH)) (i.e., that I_(cell)≥I_(Th)) the memory circuit400, 450 may again modify the RESET pulse in block 611. In this manner,by repeatedly performing the operations of blocks 611, 604, 606, and608, the memory circuit 400, 450 may successively modify the RESET pulse(e.g., strength the RESET pulse) until the PCRAM cell current (e.g.,I_(cell)) is determined to be less than the selected RESET verificationcurrent condition (e.g., I_(TH)) (i.e., until I_(cell)<I_(Th) and theselected RESET verification current condition is met).

FIG. 6B is a process flow diagram illustrating a method 621 fordetermining a type of a received configuration change command andselecting a RESET verification current condition, according to variousembodiments of the present disclosure. With reference to FIGS. 1-6B, invarious embodiments, the operations of method 621 may be performed by amemory circuit, such as memory circuit 400, 450, including a PCRAMstructure, such as PCRAM structure 10. The operations of method 621 maybe performed as part of a method for configuring a PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10, according to various embodimentsof the present disclosure, such as part of the operations of method 600(FIG. 6A). As a specific example, the operations of method 621 may beperformed as part of the operations of blocks 504 and 602 of method 600(FIG. 6A), such as in response to receiving a configuration changecommand associated with a PCRAM cell in block 502.

As discussed above, in block 512, the memory circuit 400, 450 maydetermine whether the received configuration change command is a SLCmode to MLC mode type configuration change command or a MLC mode to SLCmode type configuration change command.

In response to determining the received configuration change command isa SLC mode to MLC mode type configuration change command, in block 624,the memory circuit 400, 450 may select a first RESET verificationcurrent condition. In response to determining the received configurationchange command is a MLC mode to SLC mode type configuration changecommand, in block 626, the memory circuit 400, 450 may select a secondRESET verification current condition. As discussed with reference toblock 602 of method 600 (FIG. 6A), in some embodiments, a RESETverification condition, such as the first RESET verification currentcondition having a lower current value threshold (e.g., I_(TH)), may beconsidered to be associated with a stronger RESET and may be associatedwith a SLC mode to MLC mode type configuration change command. Incontrast, a RESET verification condition, such as the second RESETverification current condition having a higher current value threshold(e.g., I_(TH)), may be considered to be associated with a weaker RESETand may be associated with a MLC mode to SLC mode type configurationchange command. As one example, the association may be indicated by thestorage location (e.g., a location in I/O buffer 405) of the RESETverification conditions, with the first RESET verification conditionbeing stored in a location associated with SLC mode to MLC mode typeconfiguration change commands and the second RESET verificationcondition being stored in a location associated with MLC mode to SLCmode type configuration change commands. Based on determining the typeof the received configuration change command, the corresponding RESETverification condition may be selected (e.g., loaded, used, etc.).

In response to selecting the first RESET verification condition in block624 or selecting the second RESET verification condition in block 626,the memory circuit 400, 450 may program the PCRAM cell using the RESETprogram condition in block 604 of method 600 (FIG. 6A) as describedabove.

FIG. 6C is a process flow diagram illustrating a method 615 forconfiguring a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, according to various embodiments of the present disclosure. Withreference to FIGS. 1-6C, in various embodiments, the operations ofmethod 615 may be performed by a memory circuit, such as memory circuit400, 450, including a PCRAM structure, such as PCRAM structure 10. Theoperations of method 615 may be similar to the operations of methods 500(FIG. 5A), 510 (FIG. 5B), 600 (FIG. 6A), and/or 621 (FIG. 6B) describedabove, except that rather than verification based on PCRAM cell current,the operations of method 615 may provide an alternative approach inwhich PCRAM cell voltage and RESET verification voltage conditions maybe used to verify the successful RESET of the PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10.

In blocks 502 and 504, the memory circuit 400, 450 may performoperations of like numbered blocks of method 500 (FIG. 5A) to receive aconfiguration change command associated with a PCRAM cell and determinea type of the received configuration change command as discussed above.

In block 616, the memory circuit 400, 450 may select, based at least inpart on the determined type of the received configuration changecommand, a RESET verification voltage condition from a plurality ofstored RESET verification voltage conditions. In various embodiments, aplurality of different verification voltage conditions may be associatedwith different types of configuration change commands. For example,buffers or other storage devices, such as I/O buffers 405, may store aplurality of different verification voltage conditions, each associatedwith different types of configuration change commands. As a specificexample, one location may store a RESET verification voltage conditionassociated with a MLC mode to SLC mode type configuration change commandand another location may store a RESET verification voltage conditionassociated with a SLC mode to MLC mode type configuration changecommand. In various embodiments, the RESET verification voltageconditions may be cell voltage value thresholds (e.g., V_(TH))configured such that the PCRAM cell voltage (e.g., V_(cell)) may beabove the cell voltage value thresholds (e.g., V_(TH)) when the PCRAMcell, such as a PCRAM cell 100 of a PCRAM structure 10, is successfullyRESET. As a specific example, a cell voltage value threshold (e.g.,V_(TH)) may have a voltage value in a range of 0.5 V to 1.5 V, such as0.5 V, 0.5 V to 1.0 V, 1.0 V, 1.0 V to 1.5 V, 1.5 V, etc.; althoughlesser and greater voltages may also be used.

As a specific example, the plurality of RESET verification voltageconditions may be at least two RESET verification voltage conditions,such as a first RESET verification voltage condition and a second RESETverification voltage condition. The different RESET verification voltageconditions, such as the first RESET verification voltage condition andthe second RESET verification voltage condition, may each be associatedwith a type of configuration change command. For example, the firstRESET verification current condition may be associated with a SLC modeto MLC mode type configuration change command and the second RESETverification current condition may be associated with a MLC mode to SLCmode type configuration change command.

The different RESET verification voltage conditions, such as the firstRESET verification voltage condition and the second RESET verificationvoltage condition, may each be different voltage value thresholds (e.g.,V_(TH)). The voltage value thresholds (e.g., V_(TH)) may be voltagevalues, such as a selected number of volts (V), that the cell voltage(e.g., V_(Cell)) should be above to indicate that the PCRAM cell, suchas a PCRAM cell 100 of a PCRAM structure 10, was successfully RESET. Insome embodiments, when comparing two RESET verification voltageconditions, such as the first RESET verification voltage condition andthe second RESET verification voltage condition, the RESET verificationvoltage condition that is the higher voltage value threshold (e.g.,V_(TH)) may be considered to be associated with a stronger RESET of thePCRAM cell, such as a PCRAM cell 100 of a PCRAM structure 10, than theother RESET verification voltage with the lower voltage value threshold(e.g., V_(TH)). The other RESET verification voltage condition with thelower voltage value threshold (e.g., V_(TH)) may be considered to beassociated with a weaker RESET of the PCRAM cell, such as a PCRAM cell100 of a PCRAM structure 10, in comparison to the RESET verificationvoltage condition with the higher voltage value threshold (e.g.,V_(TH)). In some embodiments, a RESET verification voltage condition,such as the first RESET verification voltage condition, having a highervoltage value threshold (e.g., V_(TH)) may be associated with a SLC modeto MLC mode type configuration change command and a RESET verificationvoltage condition, such as the second RESET verification voltagecondition, having a lower voltage value (e.g., V_(TH)) may be associatedwith a MLC mode to SLC mode type configuration change command.

In block 604, the memory circuit 400, 450 may perform operations of likenumbered block of method 600 (FIG. 6A) to program the PCRAM cell using aRESET pulse as discussed above.

In block 617, the memory circuit 400, 450 may determine a PCRAM cellvoltage. For example, the controller 401 of the memory circuit 400, 450may control a voltage sensing circuit (e.g., voltage sensing circuit407) to sense the voltage of the PCRAM cell (e.g., V_(cell)) when aselected read current (e.g., I_(read)) is applied to the PCRAM cell 100.The controller 401 of the memory circuit 400, 450 may store thedetermined voltage (e.g., V_(cell)) in a buffer, such as I/O buffer 405.

In block 619, the memory circuit 400, 450 may determine whether thedetermined PCRAM cell voltage is greater than the selected RESETverification voltage condition. For example, the controller 401 of thememory circuit 400, 450 may compare the determined voltage of the PCRAMcell (e.g., V_(cell)) to the voltage value threshold (e.g., V_(TH)) ofthe selected RESET verification voltage condition, such as the firstRESET verification voltage condition or the second RESET verificationvoltage condition, to determine whether the determined PCRAM cellvoltage (e.g., V_(cell)) is greater than the selected RESET verificationvoltage condition (e.g., V_(TH)). Comparing the determined voltage ofthe PCRAM cell (e.g., V_(cell)) to the voltage value threshold (e.g.,V_(TH)) of the selected RESET verification voltage condition may be donein any manner, such as by subtracting the voltage value threshold (e.g.,V_(TH)) of the selected RESET verification voltage condition from thedetermined voltage of the PCRAM cell (V_(cell)) and determining that anon-zero positive result indicates the determined PCRAM cell voltage(e.g., V_(cell)) is greater than the selected RESET verification voltagecondition (e.g., V_(TH)) and a zero or negative result indicates thedetermined PCRAM cell voltage (e.g., V_(cell)) is less than or equal tothe selected RESET verification voltage condition (e.g., V_(TH)).Comparing the determined voltage of the PCRAM cell (e.g., V_(cell)) tothe voltage value threshold (e.g., V_(TH)) of the selected RESETverification voltage condition may enable the controller 401 of thememory circuit 400, 450 to determine whether or not the determined PCRAMcell voltage meets the selected RESET verification voltage condition.The determined PCRAM cell voltage (e.g., V_(cell)) being greater thanthe selected RESET verification voltage condition (e.g., V_(TH)) (i.e.,that V_(cell)>V_(Th)) may indicate to the controller 401 of the memorycircuit 400, 450 that the determined PCRAM cell voltage (e.g., V_(cell))meets the selected RESET verification voltage condition (e.g., V_(TH)).The determined PCRAM cell voltage (e.g., V_(cell)) not being greaterthan the selected RESET verification voltage condition (e.g., V_(TH))(i.e., that V_(cell)≤V_(Th)) may indicate to the controller 401 of thememory circuit 400, 450 that the determined PCRAM cell voltage (e.g.,V_(cell)) does not meet the selected RESET verification voltagecondition (e.g., V_(TH)).

In response to determining that the determined PCRAM cell voltage (e.g.,V_(cell)) is greater than the selected RESET verification voltagecondition (e.g., V_(TH)) (i.e., that V_(cell)>V_(Th)) the memory circuit400, 450 may, in block 613, perform operations of like numbered block ofmethod 600 (FIG. 6A) to indicate the RESET is verified as discussedabove.

In response to determining that the determined PCRAM cell voltage (e.g.,V_(cell)) is not greater than the selected RESET verification voltagecondition (e.g., V_(TH)) (i.e., that V_(cell)≤V_(Th)) the memory circuit400, 450 may, in block 611, perform operations of like numbered block ofmethod 600 (FIG. 6A) to modify the RESET pulse.

In response to modifying the RESET pulse, the memory circuit 400, 450may program the PCRAM cell using a RESET pulse, i.e., the now modifiedRESET pulse, in block 604. For example, a memory controller, such ascontroller 401 of memory circuit 400, 450, may issue a program waveformaccording to the modified RESET pulse. As a specific example, thecontroller 401 of memory circuit 400, 450 may transmit signals to therow decoder 402, column selector 403, and/or read/write driver 404 tocause the row decoder 402, column selector 403, and/or read/write driver404 to generate a program waveform having the modified current amplitudeand/or pulse width duration as modified in block 611. As discussedabove, in response to determining that the determined PCRAM cell voltage(e.g., V_(cell)) is greater than the selected RESET verification voltagecondition (e.g., V_(TH)) (i.e., that V_(cell)>V_(Th)) the memory circuit400, 450 may indicate the RESET is verified in block 613 (i.e., theselected RESET verification voltage condition (e.g., V_(TH)) is met) andin response to determining that the determined PCRAM cell voltage (e.g.,V_(cell)) is not greater than the selected RESET verification voltagecondition (e.g., V_(TH)) (i.e., that V_(cell)≤V_(Th)) the memory circuit400, 450 may again modify the RESET pulse in block 611. In this manner,by repeatedly performing the operations of blocks 611, 604, 617, and619, the memory circuit 400, 450 may successively modify the RESET pulse(e.g., strength the RESET pulse) until the PCRAM cell voltage (e.g.,V_(cell)) is determined to be greater than the selected RESETverification voltage condition (e.g., V_(TH)) (i.e., untilV_(cell)>V_(Th) and the selected RESET verification voltage condition ismet).

FIG. 6D is a process flow diagram illustrating a method 631 fordetermining a type of a received configuration change command andselecting a RESET verification voltage condition, according to variousembodiments of the present disclosure. With reference to FIGS. 1-6D, invarious embodiments, the operations of method 631 may be performed by amemory circuit, such as memory circuit 400, 450, including a PCRAMstructure, such as PCRAM structure 10. The operations of method 631 maybe performed as part of a method for configuring a PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10, according to various embodimentsof the present disclosure, such as part of the operations of method 615(FIG. 6C). As a specific example, the operations of method 631 may beperformed as part of the operations of blocks 504 and 616 of method 615(FIG. 6C), such as in response to receiving a configuration changecommand associated with a PCRAM cell in block 502.

As discussed above, in block 512, the memory circuit 400, 450 maydetermine whether the received configuration change command is a SLCmode to MLC mode type configuration change command or a MLC mode to SLCmode type configuration change command.

In response to determining the received configuration change command isa SLC mode to MLC mode type configuration change command, in block 633,the memory circuit 400, 450 may select a first RESET verificationvoltage condition. In response to determining the received configurationchange command is a MLC mode to SLC mode type configuration changecommand, in block 635, the memory circuit 400, 450 may select a secondRESET verification voltage condition. As discussed with reference toblock 616 of method 615 (FIG. 6C), in some embodiments, a RESETverification condition, such as the first RESET verification voltagecondition having a higher voltage value threshold (e.g., V_(TH)), may beconsidered to be associated with a stronger RESET and may be associatedwith a SLC mode to MLC mode type configuration change command. Incontrast, a RESET verification condition, such as the second RESETverification voltage condition having a lower voltage value threshold(e.g., V_(TH)), may be considered to be associated with a weaker RESETand may be associated with a MLC mode to SLC mode type configurationchange command. As one example, the association may be indicated by thestorage location (e.g., a location in I/O buffer 405) of the RESETverification conditions, with the first RESET verification conditionbeing stored in a location associated with SLC mode to MLC mode typeconfiguration change commands and the second RESET verificationcondition being stored in a location associated with MLC mode to SLCmode type configuration change commands. Based on determining the typeof the received configuration change command, the corresponding RESETverification condition may be selected (e.g., loaded, used, etc.).

In response to selecting the first RESET verification condition in block633 or selecting the second RESET verification condition in block 635,the memory circuit 400, 450 may program the PCRAM cell using the RESETprogram condition in block 604 of method 615 (FIG. 6C) as describedabove.

FIG. 7A is a process flow diagram illustrating a method 780 forconfiguring a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, according to various embodiments of the present disclosure. Withreference to FIGS. 1-7A, in various embodiments, the operations ofmethod 780 may be performed by a memory circuit, such as memory circuit400, 450, including a PCRAM structure, such as PCRAM structure 10. Insome embodiments, the operations of method 780 may be performed inconjunction with the operations of methods 500 (FIG. 5A), 510 (FIG. 5B),600 (FIG. 6A), 621 (FIG. 6B), 615 (FIG. 6C), and/or 631 (FIG. 6D)described above. For example, the operations of method 780 may beperformed in response to programming the PCRAM cell successfully inblock 508 of method 500 (FIG. 5A), block 613 of method 600 (FIG. 6A), orblock 613 of method 615 (FIG. 6C). In some embodiments, the operationsof method 780 may be performed independent of the method used to programthe PCRAM cell.

In block 782, the memory circuit 400, 450 may determine a RESET programoperation is to be performed for the PCRAM cell. In some embodiments, ahost device, such as a host controller or processor, may issue a RESETcommand to a memory controller, such as controller 401 of memory circuit400, 450, to cause the memory controller to perform a RESET programoperation for a memory structure, such as a PCRAM cell 100 of a PCRAMstructure 10 that is part of a memory structure 20 having a plurality ofPCRAM cells 100 (e.g., an array of PCRAM cells 100).

In block 784, the memory circuit 400, 450 may determine whether thePCRAM cell is in a SLC mode or a MLC mode. For example, the controller401 of memory circuit 400, 450 may store an indication, such as a flagsetting in the I/O buffer 405, indicating whether the last RESET programoperation transitioned from SLC to MLC or MLC to SLC. As anotherexample, the controller 401 of memory circuit 400, 450 may store anindication, such as a flag setting in the I/O buffer 405, indicating thecurrent mode, such as SLC or MLC, of a PCRAM cell, such as a PCRAM cell100 of a PCRAM structure 10. By reading the status of the indication,the controller 401 of memory circuit 400, 450 may determine the state ofthe PCRAM cell as in a SLC mode or a MLC mode.

In block 786, the memory circuit 400, 450 may select a RESET programcondition from a plurality of stored RESET program conditions based atleast in part on whether the PCRAM cell is in the SLC mode or the MLCmode. In various embodiments, a plurality of different RESET programconditions may be associated with different modes of operation of aPCRAM cell, such as SLC modes and MLC modes. For example, buffers orother storage devices, such as I/O buffers 405, may store a plurality ofdifferent RESET program conditions, each associated with different modesof operation of a PCRAM cell, such as SLC modes and MLC modes. As aspecific example, one location may store a RESET program conditionassociated with a MLC mode and another location may store a RESETprogram condition associated with a SLC mode.

As discussed above with reference to block 506 of method 500 (FIG. 5A),in various embodiments, the RESET program conditions may be configuredsuch that when selected and used (e.g., loaded, accessed, etc.), a RESETprogram condition causes a memory controller, such as controller 401 ofmemory circuit 400, 450, to generate a waveform having a currentamplitude of a current value indicated by the RESET program conditionand/or a pulse width indicated by the RESET program condition. As aspecific example, the plurality of RESET program conditions may be atleast two RESET program conditions, such as a first RESET programcondition configured to generate a first waveform having a first currentamplitude and a first pulse width and a second RESET program conditionconfigured to generate a second waveform having a second currentamplitude and a second pulse width. The different RESET programconditions, such as the first RESET program condition and the secondRESET program condition, may be configured to generate different waveforms, such as the first waveform and the second waveform.

In some embodiments, the different RESET program conditions, such as thefirst RESET program condition and the second RESET program condition,may each be associated with a different mode of the PCRAM cell. Forexample, the first RESET program condition may be associated with a MLCmode and the second RESET program condition may be associated with a SLCmode.

As discussed above with reference to block 506 of method 500 (FIG. 5A),the different wave forms, such as the first waveform and the secondwaveform, may have different current amplitude values and/or differenttime durations. As discussed above with reference to block 506 of method500 (FIG. 5A), regardless of the configuration, in some embodiments,when comparing two RESET program conditions, such as the first RESETprogram condition and the second RESET program condition, the RESETprogram condition with a higher current value for the waveform generatedby that RESET program condition may be considered to impart a strongerRESET than the other RESET program condition with the lower currentvalue for the waveform generated by that other RESET program condition.

In some embodiments, a RESET program condition, such as the first RESETprogram condition, having higher current value (e.g., imparting astronger RESET) may be associated with a MLC mode and a RESET programcondition, such as the second RESET program condition, having lowercurrent value (e.g., imparting a weaker RESET) may be associated with aSLC mode

In block 788, the memory circuit 400, 450 may program the PCRAM cellusing the selected RESET program condition. For example, a memorycontroller, such as controller 401 of memory circuit 400, 450, may issueone or more program waveforms according to the selected RESET programcondition. As a specific example, the controller 401 of memory circuit400, 450 may transmit signals to the row decoder 402, column selector403, and/or read/write driver 404 to cause the row decoder 402, columnselector 403, and/or read/write driver 404 to generate one or moreinstances of the program waveform according to the selected RESETprogram condition, such as one or more instances of the first waveformgenerated by the first RESET program condition or one or more instancesof the second waveform generated by the second RESET program condition.

FIG. 7B is a process flow diagram illustrating a method 790 forprogramming a PCRAM cell, according to various embodiments of thepresent disclosure. With reference to FIGS. 1-7B, in variousembodiments, the operations of method 790 may be performed by a memorycircuit, such as memory circuit 400, 450, including a PCRAM structure,such as PCRAM structure 10. The operations of method 790 may beperformed as part of a method for configuring a PCRAM cell, such as aPCRAM cell 100 of a PCRAM structure 10, according to various embodimentsof the present disclosure, such as part of the operations of method 780(FIG. 7A). As a specific example, the operations of method 790 may beperformed as part of the operations of blocks 786 and 788 of method 780(FIG. 7A), such as in response to determining whether the PCRAM cell isin a SLC mode or a MLC mode in block 784.

In response to determining that the PCRAM cell is in a MLC mode, inblock 514, the memory circuit 400, 450 may select a second RESET programcondition as discussed above with reference to method 510 (FIG. 5B). Inresponse to determining that the PCRAM cell is in a SLC mode, in block516, the memory circuit 400, 450 may select a second RESET programcondition as discussed above with reference to method 510 (FIG. 5B). Asdiscussed with reference to block 786 of method 780 (FIG. 7A), in someembodiments, a RESET program condition, such as the first RESET programcondition, having higher current value (e.g., imparting a strongerRESET) may be associated with a MLC mode and a RESET program condition,such as the second RESET program condition, having lower current value(e.g., imparting a weaker RESET) may be associated with SLC mode. As oneexample, the association may be indicated by the storage location (e.g.,a location in I/O buffer 405) of the RESET program conditions, with thefirst RESET program condition being stored in a location associated witha MLC mode and the second RESET program condition being stored in alocation associated with a SLC mode. Based on determining the currentmode setting of the PCRAM cell, the corresponding RESET programcondition may be selected (e.g., loaded, used, etc.).

In response to selecting the second RESET program condition, the memorycircuit 400, 450 may program the PCRAM cell to a HRS using the secondRESET program condition in block 792. For example, a memory controller,such as controller 401 of memory circuit 400, 450, may issue one or moreprogram waveforms according to the second RESET program condition. As aspecific example, the controller 401 of memory circuit 400, 450 maytransmit signals to the row decoder 402, column selector 403, and/orread/write driver 404 to cause the row decoder 402, column selector 403,and/or read/write driver 404 to generate one or more instances of thesecond waveform generated by the second RESET program condition.

In response to selecting the first RESET program condition, the memorycircuit 400, 450 may program the PCRAM cell to an intermediate stateassociated with the RESET program operation using incremental step pulseprogramming initiated at the first RESET program condition in block 794.In some embodiments, programming the PCRAM cell to an intermediate stateassociated with the RESET program operation may include firstprogramming the PCRAM cell to a HRS, such as an HRS using the firstRESET program condition, and then programing the PCRAM cell to anintermediate state using incremental step pulse programming. Forexample, a memory controller, such as controller 401 of memory circuit400, 450, may issue one or more program waveforms according to the firstRESET program condition. In response to using the one or more programwaveforms according to the first RESET program condition, the memorycontroller, such as controller 401 of memory circuit 400, 450, mayverify whether the intermedia state was achieved. In response todetermining the intermediate state was not achieved, the memorycontroller, such as controller 401 of memory circuit 400, 450, may issuea series of write and read pulses in a program-verify sequence (orapproach) until the intermediate state is determined to be achieved. Theseries of write pulses may be adjusted (e.g., pulse width and/or currentamplitude increased, decreased, etc.) incrementally by the memorycontroller, such as controller 401 of memory circuit 400, 450, therebyimplementing incremental step pulse programming until the intermediatestate is determined to be achieved. As a specific example, thecontroller 401 of memory circuit 400, 450 may transmit signals to therow decoder 402, column selector 403, and/or read/write driver 404 tocause the row decoder 402, column selector 403, and/or read/write driver404 to generate one or more instances of the first waveform generated bythe first RESET program condition. Programming to the HRS using thefirst RESET program condition may be a strong RESET operation conduciveto MCL programing and upon achieving the HRS using the first RESETprogram condition, the controller 401 of memory circuit 400, 450 maytransmit signals to the row decoder 402, column selector 403, and/orread/write driver 404 to cause the row decoder 402, column selector 403,and/or read/write driver 404 to program an intermediate state, such as afirst intermediate state (e.g., MCL1) or second intermediate state(e.g., MCL2), using incremental step pulse programming to adjust andreapply, the waveform, until the program-verify sequency (or approach)achieves the intermediate state, such as a first intermediate state(e.g., MCL1) or second intermediate state (e.g., MCL2).

FIG. 8 is a process flow diagram illustrating a method 800 forprogramming a PCRAM cell, such as a PCRAM cell 100 of a PCRAM structure10, according to various embodiments of the present disclosure. Withreference to FIGS. 1-8 , in various embodiments, the operations ofmethod 800 may be performed by a memory circuit, such as memory circuit400, 450, including a PCRAM structure, such as PCRAM structure 10. Theoperations of method 800 may be performed in conjunction with operationsof any of methods 500, 510, 600, 621, 615, 631, 780, and/or 790.

In block 802, the memory circuit 400, 450 may receive a neural networklayer execution indication. For example, the neural network controller451 may receive neural network layer execution indications, from a hostcontroller or processor. A neural network layer execution indication maybe an indication that one or more computations for a next layer of aneural network are to be executed by the circuit 450, such as by one ormore PCRAM cell 100 of the circuit 450. The neural network layerexecution indication may indicate the type of neural network layer to beexecuted and/or an error tolerance for the neural network layer. As oneexample, the neural network controller 451 may receive a neural networklayer execution indication indicating a type of a next layer to beexecuted for a neural network.

In block 804, the memory circuit 400, 450 may determine whether an errortolerance for the neural network layer supports MLC mode operation for aPCRAM cell, such as PCRAM cell 100. For example, the network controller451 may perform operations to determine an error tolerance associatedwith the type of the next layer to be executed for the neural network,such as by retrieving the value of an error tolerance from a memoryand/or parsing the neural network layer execution indication when theerror tolerance is included in the neural network execution indication.As one specific example, the determined error tolerance may be comparedto a threshold for error tolerance associated with MLC mode operation,and the determined error tolerance being higher than the threshold forerror tolerance associated with MLC mode operation may indicate theerror tolerance supports MLC mode. The determined error tolerance beingat or below the threshold for error tolerance associated with MLC modeoperation may indicate the error tolerance does not support MLC mode.

In response to determining that the error tolerance supports MLC mode,the memory circuit 400, 450 may determine whether the PCRAM cell is inMLC mode in block 806. As an example, the neural network controller 451may track and/or determine the state of one or more PCRAM cells 100 inthe circuit 450, such as whether any PCRAM cell 100 is in a SLC modeand/or a MLC mode. For example, the neural network controller 451 may beconfigured to perform operations to determine whether a PCRAM cell 100is in MLC mode or SLC mode in response to determining error tolerancesupports MLC mode. In response to determining the PCRAM cell is alreadyin MLC mode, the memory circuit 400, 450 may take no action in block810. In response to determining the PCRAM cell is in SLC mode, thememory circuit 400, 450 may generate a SLC mode to MLC mode typeconfiguration change command in block 812. In block 816, the memorycircuit 400, 450 may send the configuration change command associatedwith the PCRAM cell. For example, the configuration change commandassociated with the PCRAM cell may be sent from the neural networkcontroller 451 to the controller 401 and received by the controller 401as discussed above with reference to block 502.

In response to determining that the error tolerance does not support MLCmode, the memory circuit 400, 450 may determine whether the PCRAM cellis in SLC mode in block 808. As an example, the neural networkcontroller 451 may track and/or determine the state of one or more PCRAMcells 100 in the circuit 450, such as whether any PCRAM cell 100 is in aSLC mode and/or a MLC mode. For example, the neural network controller451 may be configured to perform operations to determine whether a PCRAMcell 100 is in SLC mode or MLC mode in response to determining errortolerance does not support MLC mode. In response to determining thePCRAM cell is already in SLC mode, the memory circuit 400, 450 may takeno action in block 810. In response to determining the PCRAM cell is inMLC mode, the memory circuit 400, 450 may generate a MLC mode to SLCmode type configuration change command in block 814. In block 816, thememory circuit 400, 450 may send the configuration change commandassociated with the PCRAM cell. For example, the configuration changecommand associated with the PCRAM cell may be sent from the neuralnetwork controller 451 to the controller 401 and received by thecontroller 401 as discussed above with reference to block 502.

Various embodiments provide methods for configuring a phase-changerandom-access memory (PCRAM) cell. Various embodiments may achievetighter MLC resistance distribution in a MLC mode and/or lower programenergy consumption in a SLC mode compared to conventional RESEToperations.

Various embodiments may provide a method for configuring a phase-changerandom-access memory (PCRAM) cell (100) including receiving aconfiguration change command associated with the PCRAM cell (100),determining a type of the received configuration change command,selecting, based at least in part on the determined type of the receivedconfiguration change command, a RESET program condition from a pluralityof stored RESET program conditions, and programming the PCRAM cell (100)using the selected RESET program condition. In some embodiments, theplurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude. In some embodiments, the first pulse width has alonger time duration than the second pulse width. In some embodiments,determining the type of the received configuration change command mayinclude determining whether the received configuration change command isa single-level-cell (SLC) mode to multi-level-cell (MLC) mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command, and selecting, based at least in part onthe determined type of the received configuration change command, theRESET program condition from the plurality of stored RESET programconditions may include selecting the first RESET program condition inresponse to determining that the received configuration change commandis a SLC mode to MLC mode type configuration change command, andselecting the second RESET program condition in response to determiningthat the received configuration change command is a MLC mode to SLC modetype configuration change command. In some embodiments, the firstcurrent amplitude has a higher current value than the second currentamplitude and the first pulse width has a longer time duration than thesecond pulse width. In some embodiments, the method may further include,after programming the PCRAM cell (100) using the selected RESET programcondition, determining a RESET program condition operation is to beperformed for the PCRAM cell (100), determining whether the PCRAM cell(100) is in a SLC mode or a MLC mode in response to determining theRESET program condition operation is to be performed for the PCRAM cell(100), in response to determining that the PCRAM cell (100) is in theSLC mode, selecting the second RESET program condition, and programmingthe PCRAM cell (100) to a high resistance state (HRS) using the secondRESET program condition, and in response to determining that the PCRAMcell (100) is in the MLC mode, selecting the first RESET programcondition, and programming the PCRAM cell (100) to an intermediate stateassociated with the RESET program condition operation using incrementalstep pulse programming initiated at the first RESET program condition.In some embodiments, the first current amplitude has a higher currentvalue than the second current amplitude and the first pulse width has alonger time duration than the second pulse width.

Various embodiments may include a memory device (400, 450) including aphase-change random-access memory (PCRAM) cell (100), a current sensingcircuit (406), and a controller (401) configured to receive aconfiguration change command associated with the PCRAM cell (100),determine a type of the received configuration change command, select,based at least in part on the determined type of the receivedconfiguration change command, a RESET program condition from a pluralityof stored RESET program conditions, and program the PCRAM cell (100)using the selected RESET program condition. In some embodiments, theplurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude. In some embodiments, the first pulse width has alonger time duration than the second pulse width. In some embodiments,the controller (401) may be further configured such that determining thetype of the received configuration change command may includedetermining whether the received configuration change command is asingle-level-cell (SLC) mode to multi-level-cell (MLC) mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command, and selecting, based at least in part onthe determined type of the received configuration change command, theRESET program condition from the plurality of stored RESET programconditions may include selecting the first RESET program condition inresponse to determining that the received configuration change commandis a SLC mode to MLC mode type configuration change command, andselecting the second RESET program condition in response to determiningthat the received configuration change command is a MLC mode to SLC modetype configuration change command. In some embodiments, the firstcurrent amplitude has a higher current value than the second currentamplitude and the first pulse width has a longer time duration than thesecond pulse width. In some embodiments, the controller (401) may befurther configured to, after programming the PCRAM cell (100) using theselected RESET program condition, determine a RESET program conditionoperation is to be performed for the PCRAM cell (100), determine whetherthe PCRAM cell (100) is in a SLC mode or a MLC mode in response todetermining the RESET program condition operation is to be performed forthe PCRAM cell (100), in response to determining that the PCRAM cell(100) is in the SLC mode, select the second RESET program condition, andprogram the PCRAM cell (100) to a high resistance state (HRS) using thesecond RESET program condition, and in response to determining that thePCRAM cell (100) is in the MLC mode, select the first RESET programcondition, and program the PCRAM cell (100) to an intermediate stateassociated with the RESET program condition operation using incrementalstep pulse programming initiated at the first RESET program condition.In some embodiments, the first current amplitude has a higher currentvalue than the second current amplitude and the first pulse width has alonger time duration than the second pulse width.

Various embodiments may provide a method for configuring a phase-changerandom-access memory (PCRAM) cell (100) including receiving aconfiguration change command associated with the PCRAM cell (100),determining a type of the received configuration change command,selecting, based at least in part on the determined type of the receivedconfiguration change command, a RESET verification condition from aplurality of stored RESET verification conditions (e.g., a RESETverification current condition from a plurality of stored RESETverification current conditions, a RESET verification voltage conditionfrom a plurality of stored RESET verification voltage conditions, etc.),programming the PCRAM cell (100) using a RESET pulse, determining aPCRAM cell (100) condition (e.g., a PCRAM cell (100) current, a PCRAMcell (100) voltage, etc.) in response to programming the PCRAM cell(100) using the RESET pulse, determining whether the determined PCRAMcell (100) condition meets the selected RESET verification condition(e.g., determining whether the determined PCRAM cell (100) current isless than the selected RESET verification current condition, determiningwhether the determined PCRAM cell (100) voltage is greater than theselected RESET verification voltage condition, etc.), modifying theRESET pulse to increase one or both of its current amplitude and itspulse width in response to determining the PCRAM cell (100) conditiondoes not meet the selected RESET verification condition, and programmingthe PCRAM cell (100) using the modified RESET pulse. In someembodiments, the plurality of stored RESET verification conditionsincludes a first RESET verification current condition having a firstcurrent value and a second RESET verification current condition having asecond current value or the plurality of stored RESET verificationconditions includes a first RESET verification voltage condition havinga first voltage value and a second RESET verification voltage conditionhaving a second voltage value. In some embodiments determining the typeof the received configuration change command includes determiningwhether the received configuration change command is a single-level-cell(SLC) mode to multi-level-cell (MLC) mode type configuration changecommand or a MLC mode to SLC mode type configuration change command, andselecting, based at least in part on the determined type of the receivedconfiguration change command, the RESET verification condition from theplurality of stored RESET verification conditions includes selecting afirst RESET verification condition in response to determining that thereceived configuration change command is a SLC mode to MLC mode typeconfiguration change command, and selecting a second RESET verificationcondition in response to determining that the received configurationchange command is a MLC mode to SLC mode type configuration changecommand. In some embodiments a first current value of the first RESETverification condition is a lower current value than a second currentvalue of the second RESET verification condition or a first voltagevalue of the first RESET verification condition is a higher voltagevalue than a second voltage value of the second RESET verificationcondition. In some embodiments, the method further includes, in responseto programming the PCRAM cell (100) using the modified RESET pulse andsuccessively until the PCRAM cell (100) condition is determined to meetthe selected RESET verification condition, determining the PCRAM cell(100) condition, determining whether the determined PCRAM cell (100)condition meets the selected RESET verification condition, modifying themodified RESET pulse to increase one or both of its current amplitudeand its pulse width in response to determining the PCRAM cell (100)current does not meet the selected RESET verification condition, andprogramming the PCRAM cell (100) using the modified RESET pulse. In someembodiments, the method further includes after determining the PCRAMcell (100) meets the selected RESET verification condition, determininga RESET program operation is to be performed for the PCRAM cell (100),determining whether the PCRAM cell (100) is in a SLC mode or a MLC modein response to determining the RESET program operation is to beperformed for the PCRAM cell (100), in response to determining that thePCRAM cell (100) is in the MLC mode, selecting a first RESET programcondition, and programming the PCRAM cell (100) to an intermediate stateassociated with the RESET program operation using incremental step pulseprogramming initiated at the first RESET program condition, and inresponse to determining that the PCRAM cell (100) is in the SLC mode,selecting a second RESET program condition; and programming the PCRAMcell (100) to a high resistance state (HRS) using the second RESETprogram condition. In some embodiments the first RESET program conditionis configured to generate a first waveform having a first currentamplitude and a first pulse width, the second RESET program condition isconfigured to generate a second waveform having a second currentamplitude and a second pulse width, and the first current amplitude hasa higher current value than the second current amplitude and the firstpulse width has a longer time duration than the second pulse width.

Various embodiments may include a memory device (400, 450) including aphase-change random-access memory (PCRAM) cell (100), a current sensingcircuit (406) and/or voltage sensing circuit (407), and a controller(401) configured to receive a configuration change command associatedwith the PCRAM cell (100), determine a type of the receivedconfiguration change command, select, based at least in part on thedetermined type of the received configuration change command, a RESETverification condition from a plurality of stored RESET verificationconditions (e.g., a RESET verification current condition from aplurality of stored RESET verification current conditions, a RESETverification voltage condition from a plurality of stored RESETverification voltage conditions, etc.), program the PCRAM cell (100)using a RESET pulse, determine a PCRAM cell (100) condition (e.g., aPCRAM cell (100) current, a PCRAM cell (100) voltage, etc.) in responseto programming the PCRAM cell (100) using the RESET pulse, determinewhether the determined PCRAM cell (100) condition meets the selectedRESET verification condition (e.g., determine whether the determinedPCRAM cell (100) current is less than the selected RESET verificationcurrent condition, determine whether the determined PCRAM cell (100)voltage is greater than the selected RESET verification voltagecondition, etc.), modify the RESET pulse to increase one or both of itscurrent amplitude and its pulse width in response to determining thePCRAM cell (100) condition does not meet the selected RESET verificationcurrent condition, and program the PCRAM cell (100) using the modifiedRESET pulse. In some embodiments, the plurality of stored RESETverification conditions includes a first RESET verification currentcondition having a first current value and a second RESET verificationcurrent condition having a second current value or the plurality ofstored RESET verification conditions includes a first RESET verificationvoltage condition having a first voltage value and a second RESETverification voltage condition having a second voltage value. In someembodiments, the controller (401) may be further configured such thatdetermining the type of the received configuration change commandincludes determining whether the received configuration change commandis a single-level-cell (SLC) mode to multi-level-cell (MLC) mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command, and selecting, based at least in part onthe determined type of the received configuration change command, theRESET verification condition from the plurality of stored RESETverification conditions includes selecting a RESET verificationcondition in response to determining that the received configurationchange command is a SLC mode to MLC mode type configuration changecommand, and selecting a second RESET verification condition in responseto determining that the received configuration change command is a MLCmode to SLC mode type configuration change command. In some embodimentsa first current value of the first RESET verification condition is alower current value than a second current value of the second RESETverification condition or a first voltage value of the first RESETverification condition is a higher voltage value than a second voltagevalue of the second RESET verification condition. In some embodiments,the controller (401) may be further configured to, in response toprogramming the PCRAM cell (100) using the modified RESET pulse andsuccessively until the PCRAM cell (100) condition is determined to meetthe selected RESET verification condition, determine the PCRAM cell(100) condition, determine whether the determined PCRAM cell (100)condition meets the selected RESET verification condition, modify themodified RESET pulse to increase one or both of its current amplitudeand its pulse width in response to determining the PCRAM cell (100)condition does not meet the selected RESET verification condition, andprogram the PCRAM cell (100) using the modified RESET pulse. In someembodiments, the controller (401) may be further configured to, afterdetermining the PCRAM cell (100) condition meets the selected RESETverification condition, determine a RESET program operation is to beperformed for the PCRAM cell (100), determine whether the PCRAM cell(100) is in a SLC mode or a MLC mode in response to determining theRESET program operation is to be performed for the PCRAM cell (100), inresponse to determining that the PCRAM cell (100) is in the MLC mode,select a first RESET program condition, and program the PCRAM cell (100)to an intermediate state associated with the RESET program operationusing incremental step pulse programming initiated at the first RESETprogram condition, and in response to determining that the PCRAM cell(100) is in the SLC mode, select a second RESET program condition; andprogram the PCRAM cell (100) to a high resistance state (HRS) using thesecond RESET program condition. In some embodiments the first RESETprogram condition is configured to generate a first waveform having afirst current amplitude and a first pulse width, the second RESETprogram condition is configured to generate a second waveform having asecond current amplitude and a second pulse width, and the first currentamplitude has a higher current value than the second current amplitudeand the first pulse width has a longer time duration than the secondpulse width.

Various embodiments may provide a method for configuring a phase-changerandom-access memory (PCRAM) cell (100) including determining a RESETprogram operation is to be performed for the PCRAM cell (100),determining whether the PCRAM cell (100) is in a single-level-cell (SLC)mode or a multi-level-cell (MLC) mode in response to determining theRESET program operation is to be performed for the PCRAM cell (100),selecting a RESET program condition from a plurality of stored RESETprogram conditions based at least in part on whether the PCRAM cell(100) is in the SLC mode or the MLC mode, and programming the PCRAM cell(100) using the selected RESET program condition. In some embodiments,the plurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments,selecting the RESET program condition from the plurality of stored RESETprogram conditions based at least in part on whether the PCRAM cell(100) is in the SLC mode or the MLC mode includes selecting the secondRESET program condition in response to determining that the PCRAM cell(100) is in the SLC mode, and selecting the first RESET programcondition in response to determining that the PCRAM cell (100) is in theMLC mode. In some embodiments, programming the PCRAM cell (100) usingthe selected RESET program condition includes, in response todetermining that the PCRAM cell (100) is in the SLC mode, programmingthe PCRAM cell (100) to a high resistance state (HRS) using the secondRESET program condition, and in response to determining that the PCRAMcell (100) is in the MLC mode, programming the PCRAM cell (100) to anintermediate state associated with the RESET program operation usingincremental step pulse programming initiated at the first RESET programcondition. In some embodiments, the first current amplitude has a highercurrent value than the second current amplitude and the first pulsewidth has a longer time duration than the second pulse width.

Various embodiments may include a memory device (400, 450) including aphase-change random-access memory (PCRAM) cell (100), a current sensingcircuit (406), and a controller (401) configured to determine a RESETprogram operation is to be performed for the PCRAM cell (100), determinewhether the PCRAM cell (100) is in a single-level-cell (SLC) mode or amulti-level-cell (MLC) mode in response to determining the RESET programoperation is to be performed for the PCRAM cell (100), select a RESETprogram condition from a plurality of stored RESET program conditionsbased at least in part on whether the PCRAM cell (100) is in the SLCmode or the MLC mode, and program the PCRAM cell (100) using theselected RESET program condition. In some embodiments, the plurality ofstored RESET program conditions includes a first RESET program conditionconfigured to generate a first waveform having a first current amplitudeand a first pulse width, and a second RESET program condition configuredto generate a second waveform having a second current amplitude and asecond pulse width. In some embodiments, the controller (401) may befurther configured such that selecting the RESET program condition fromthe plurality of stored RESET program conditions based at least in parton whether the PCRAM cell (100) is in the SLC mode or the MLC modeincludes selecting the second RESET program condition in response todetermining that the PCRAM cell (100) is in the SLC mode, and selectingthe first RESET program condition in response to determining that thePCRAM cell (100) is in the MLC mode. In some embodiments, the controller(401) may be further configured such that programming the PCRAM cell(100) using the selected RESET program condition includes, in responseto determining that the PCRAM cell (100) is in the SLC mode, programmingthe PCRAM cell (100) to a high resistance state (HRS) using the secondRESET program condition, and in response to determining that the PCRAMcell (100) is in the MLC mode, programming the PCRAM cell (100) to anintermediate state associated with the RESET program operation usingincremental step pulse programming initiated at the first RESET programcondition. In some embodiments, the first current amplitude has a highercurrent value than the second current amplitude and the first pulsewidth has a longer time duration than the second pulse width.

Various embodiments may provide a method for configuring a phase-changerandom-access memory (PCRAM) cell (100) including determining a type ofa configuration change command associated with the PCRAM cell (100),selecting, based at least in part on the determined type of theconfiguration change command, a RESET program condition from a pluralityof stored RESET program conditions, and programming the PCRAM cell (100)using the selected RESET program condition. In some embodiments, theconfiguration change command is generated based at least in part on anerror tolerance for a neural network layer. In some embodiments, theplurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude. In some embodiments, the first pulse width has alonger time duration than the second pulse width. In some embodiments,determining the type of the configuration change command may includedetermining whether the configuration change command is asingle-level-cell (SLC) mode to multi-level-cell (MLC) mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command, and selecting, based at least in part onthe determined type of the configuration change command, the RESETprogram condition from the plurality of stored RESET program conditionsmay include selecting the first RESET program condition in response todetermining that the configuration change command is a SLC mode to MLCmode type configuration change command, and selecting the second RESETprogram condition in response to determining that the configurationchange command is a MLC mode to SLC mode type configuration changecommand. In some embodiments, the first current amplitude has a highercurrent value than the second current amplitude and the first pulsewidth has a longer time duration than the second pulse width. In someembodiments, the method may further include, after programming the PCRAMcell (100) using the selected RESET program condition, determining aRESET program condition operation is to be performed for the PCRAM cell(100), determining whether the PCRAM cell (100) is in a SLC mode or aMLC mode in response to determining the RESET program conditionoperation is to be performed for the PCRAM cell (100), in response todetermining that the PCRAM cell (100) is in the SLC mode, selecting thesecond RESET program condition, and programming the PCRAM cell (100) toa high resistance state (HRS) using the second RESET program condition,and in response to determining that the PCRAM cell (100) is in the MLCmode, selecting the first RESET program condition, and programming thePCRAM cell (100) to an intermediate state associated with the RESETprogram condition operation using incremental step pulse programminginitiated at the first RESET program condition. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude and the first pulse width has a longer time durationthan the second pulse width.

Various embodiments may include a memory device (400, 450) including aphase-change random-access memory (PCRAM) cell (100), a current sensingcircuit (406), and a controller (401) configured to determine a type ofa configuration change command associated with the PCRAM cell (100),select, based at least in part on the determined type of theconfiguration change command, a RESET program condition from a pluralityof stored RESET program conditions, and program the PCRAM cell (100)using the selected RESET program condition. In some embodiments, theplurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude. In some embodiments, the first pulse width has alonger time duration than the second pulse width. In some embodiments,the controller (401) may be further configured such that determining thetype of the configuration change command may include determining whetherthe configuration change command is a single-level-cell (SLC) mode tomulti-level-cell (MLC) mode type configuration change command or a MLCmode to SLC mode type configuration change command, and selecting, basedat least in part on the determined type of the configuration changecommand, the RESET program condition from the plurality of stored RESETprogram conditions may include selecting the first RESET programcondition in response to determining that the configuration changecommand is a SLC mode to MLC mode type configuration change command, andselecting the second RESET program condition in response to determiningthat the configuration change command is a MLC mode to SLC mode typeconfiguration change command. In some embodiments, the first currentamplitude has a higher current value than the second current amplitudeand the first pulse width has a longer time duration than the secondpulse width. In some embodiments, the controller (401) may be furtherconfigured to, after programming the PCRAM cell (100) using the selectedRESET program condition, determine a RESET program condition operationis to be performed for the PCRAM cell (100), determine whether the PCRAMcell (100) is in a SLC mode or a MLC mode in response to determining theRESET program condition operation is to be performed for the PCRAM cell(100), in response to determining that the PCRAM cell (100) is in theSLC mode, select the second RESET program condition, and program thePCRAM cell (100) to a high resistance state (HRS) using the second RESETprogram condition, and in response to determining that the PCRAM cell(100) is in the MLC mode, select the first RESET program condition, andprogram the PCRAM cell (100) to an intermediate state associated withthe RESET program condition operation using incremental step pulseprogramming initiated at the first RESET program condition. In someembodiments, the first current amplitude has a higher current value thanthe second current amplitude and the first pulse width has a longer timeduration than the second pulse width.

Various embodiments may provide a method for configuring a phase-changerandom-access memory (PCRAM) cell (100) including determining whetherattribute of a neural network layer supports changing an operating modeof the PCRAM cell (100), and generating a configuration change commandto change the operating mode of the PCRAM cell (100) in response todetermining that attribute of the neural network layer supports changingthe operating mode of the PCRAM cell (100). In some embodiments, theattribute of the neural network layer is an error tolerance for theneural network layer. In some embodiments, the configuration changecommand is a single-level-cell (SLC) mode to multi-level-cell (MLC) modetype configuration change command. In some embodiments, theconfiguration change command is a multi-level-cell (MLC) mode tosingle-level-cell (SLC) mode type configuration change command. Someembodiments may further include receiving the configuration changecommand associated with the PCRAM cell (100), determining a type of thereceived configuration change command, selecting, based at least in parton the determined type of the received configuration change command, aRESET program condition from a plurality of stored RESET programconditions, wherein the plurality of stored RESET program conditionscomprises at least: a first RESET program condition configured togenerate a first waveform having a first current amplitude and a firstpulse width; and a second RESET program condition configured to generatea second waveform having a second current amplitude and a second pulsewidth, and programming the PCRAM cell (100) using the selected RESETprogram condition. In some embodiments, the plurality of stored RESETprogram conditions includes a first RESET program condition configuredto generate a first waveform having a first current amplitude and afirst pulse width, and a second RESET program condition configured togenerate a second waveform having a second current amplitude and asecond pulse width. In some embodiments, the first current amplitude hasa higher current value than the second current amplitude. In someembodiments, the first pulse width has a longer time duration than thesecond pulse width. In some embodiments, determining the type of thereceived configuration change command may include determining whetherthe received configuration change command is a single-level-cell (SLC)mode to multi-level-cell (MLC) mode type configuration change command ora MLC mode to SLC mode type configuration change command, and selecting,based at least in part on the determined type of the receivedconfiguration change command, the RESET program condition from theplurality of stored RESET program conditions may include selecting thefirst RESET program condition in response to determining that thereceived configuration change command is a SLC mode to MLC mode typeconfiguration change command, and selecting the second RESET programcondition in response to determining that the received configurationchange command is a MLC mode to SLC mode type configuration changecommand. In some embodiments, the first current amplitude has a highercurrent value than the second current amplitude and the first pulsewidth has a longer time duration than the second pulse width. In someembodiments, the method may further include, after programming the PCRAMcell (100) using the selected RESET program condition, determining aRESET program condition operation is to be performed for the PCRAM cell(100), determining whether the PCRAM cell (100) is in a SLC mode or aMLC mode in response to determining the RESET program conditionoperation is to be performed for the PCRAM cell (100), in response todetermining that the PCRAM cell (100) is in the SLC mode, selecting thesecond RESET program condition, and programming the PCRAM cell (100) toa high resistance state (HRS) using the second RESET program condition,and in response to determining that the PCRAM cell (100) is in the MLCmode, selecting the first RESET program condition, and programming thePCRAM cell (100) to an intermediate state associated with the RESETprogram condition operation using incremental step pulse programminginitiated at the first RESET program condition. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude and the first pulse width has a longer time durationthan the second pulse width.

Various embodiments may include a memory device (400, 450) including aphase-change random-access memory (PCRAM) cell (100), a current sensingcircuit (406), and a controller (401) configured to determine whetherattribute of a neural network layer supports changing an operating modeof the PCRAM cell (100), and generate a configuration change command tochange the operating mode of the PCRAM cell (100) in response todetermining that attribute of the neural network layer supports changingthe operating mode of the PCRAM cell (100). In some embodiments, theattribute of the neural network layer is an error tolerance for theneural network layer. In some embodiments, the configuration changecommand is a single-level-cell (SLC) mode to multi-level-cell (MLC) modetype configuration change command. In some embodiments, theconfiguration change command is a multi-level-cell (MLC) mode tosingle-level-cell (SLC) mode type configuration change command. In someembodiments, the controller (401) may be further configured to receivethe configuration change command associated with the PCRAM cell (100),determine a type of the received configuration change command, select,based at least in part on the determined type of the receivedconfiguration change command, a RESET program condition from a pluralityof stored RESET program conditions, and program the PCRAM cell (100)using the selected RESET program condition. In some embodiments, theplurality of stored RESET program conditions includes a first RESETprogram condition configured to generate a first waveform having a firstcurrent amplitude and a first pulse width, and a second RESET programcondition configured to generate a second waveform having a secondcurrent amplitude and a second pulse width. In some embodiments, thefirst current amplitude has a higher current value than the secondcurrent amplitude. In some embodiments, the first pulse width has alonger time duration than the second pulse width. In some embodiments,the controller (401) may be further configured such that determining thetype of the received configuration change command may includedetermining whether the received configuration change command is asingle-level-cell (SLC) mode to multi-level-cell (MLC) mode typeconfiguration change command or a MLC mode to SLC mode typeconfiguration change command, and selecting, based at least in part onthe determined type of the received configuration change command, theRESET program condition from the plurality of stored RESET programconditions may include selecting the first RESET program condition inresponse to determining that the received configuration change commandis a SLC mode to MLC mode type configuration change command, andselecting the second RESET program condition in response to determiningthat the received configuration change command is a MLC mode to SLC modetype configuration change command. In some embodiments, the firstcurrent amplitude has a higher current value than the second currentamplitude and the first pulse width has a longer time duration than thesecond pulse width. In some embodiments, the controller (401) may befurther configured to, after programming the PCRAM cell (100) using theselected RESET program condition, determine a RESET program conditionoperation is to be performed for the PCRAM cell (100), determine whetherthe PCRAM cell (100) is in a SLC mode or a MLC mode in response todetermining the RESET program condition operation is to be performed forthe PCRAM cell (100), in response to determining that the PCRAM cell(100) is in the SLC mode, select the second RESET program condition, andprogram the PCRAM cell (100) to a high resistance state (HRS) using thesecond RESET program condition, and in response to determining that thePCRAM cell (100) is in the MLC mode, select the first RESET programcondition, and program the PCRAM cell (100) to an intermediate stateassociated with the RESET program condition operation using incrementalstep pulse programming initiated at the first RESET program condition.In some embodiments, the first current amplitude has a higher currentvalue than the second current amplitude and the first pulse width has alonger time duration than the second pulse width.

The foregoing method descriptions and the process flow diagrams areprovided merely as illustrative examples and are not intended to requireor imply that the operations of various embodiments must be performed inthe order presented. As will be appreciated by one of skill in the artthe order of operations in the foregoing embodiments may be performed inany order. Words such as “thereafter,” “then,” “next,” etc. are notintended to limit the order of the operations; these words are used toguide the reader through the description of the methods. Further, anyreference to claim elements in the singular, for example, using thearticles “a,” “an,” or “the” is not to be construed as limiting theelement to the singular.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method for configuring a phase-changerandom-access memory (PCRAM) cell, comprising: receiving a configurationchange command associated with the PCRAM cell; determining a type of thereceived configuration change command; selecting, based at least in parton the determined type of the received configuration change command, aRESET program condition from a plurality of stored RESET programconditions; and programming the PCRAM cell using the selected RESETprogram condition.
 2. The method of claim 1, wherein the plurality ofstored RESET program conditions comprises: a first RESET programcondition configured to generate a first waveform having a first currentamplitude and a first pulse width; and a second RESET program conditionconfigured to generate a second waveform having a second currentamplitude and a second pulse width.
 3. The method of claim 2, whereinthe first current amplitude has a higher current value than the secondcurrent amplitude.
 4. The method of claim 2, wherein the first pulsewidth has a longer time duration than the second pulse width.
 5. Themethod of claim 2, wherein: determining the type of the receivedconfiguration change command comprises determining whether the receivedconfiguration change command is a single-level-cell (SLC) mode tomulti-level-cell (MLC) mode type configuration change command or a MLCmode to SLC mode type configuration change command; and selecting, basedat least in part on the determined type of the received configurationchange command, the RESET program condition from the plurality of storedRESET program conditions comprises: selecting the first RESET programcondition in response to determining that the received configurationchange command is a SLC mode to MLC mode type configuration changecommand; and selecting the second RESET program condition in response todetermining that the received configuration change command is a MLC modeto SLC mode type configuration change command.
 6. The method of claim 5,wherein the first current amplitude has a higher current value than thesecond current amplitude and the first pulse width has a longer timeduration than the second pulse width.
 7. The method of claim 5, furthercomprising, after programming the PCRAM cell using the selected RESETprogram condition: determining a RESET program condition operation is tobe performed for the PCRAM cell; determining whether the PCRAM cell isin a SLC mode or a MLC mode in response to determining the RESET programcondition operation is to be performed for the PCRAM cell; in responseto determining that the PCRAM cell is in the SLC mode: selecting thesecond RESET program condition; and programming the PCRAM cell to a highresistance state (HRS) using the second RESET program condition; and inresponse to determining that the PCRAM cell is in the MLC mode:selecting the first RESET program condition; and programming the PCRAMcell to an intermediate state associated with the RESET programcondition operation using incremental step pulse programming initiatedat the first RESET program condition.
 8. The method of claim 7, whereinthe first current amplitude has a higher current value than the secondcurrent amplitude and the first pulse width has a longer time durationthan the second pulse width.
 9. A method for configuring a phase-changerandom-access memory (PCRAM) cell, comprising: receiving a configurationchange command associated with the PCRAM cell; determining a type of thereceived configuration change command; selecting, based at least in parton the determined type of the received configuration change command, aRESET verification condition from a plurality of stored RESETverification conditions; programming the PCRAM cell using a RESET pulse;determining a PCRAM cell condition in response to programming the PCRAMcell using the RESET pulse; determining whether the determined PCRAMcell condition meets the selected RESET verification condition;modifying the RESET pulse to increase one or both of its currentamplitude and its pulse width in response to determining the determinedPCRAM cell condition does not meet the selected RESET verificationcondition; and programming the PCRAM cell using the modified RESETpulse.
 10. The method of claim 9, wherein the plurality of stored RESETverification conditions comprises: a first RESET verification currentcondition having a first current value and a second RESET verificationcurrent condition having a second current value; or a first RESETverification voltage condition having a first voltage value and a secondRESET verification voltage condition having a second voltage value. 11.The method of claim 9, wherein: determining the type of the receivedconfiguration change command comprises determining whether the receivedconfiguration change command is a single-level-cell (SLC) mode tomulti-level-cell (MLC) mode type configuration change command or a MLCmode to SLC mode type configuration change command; and selecting, basedat least in part on the determined type of the received configurationchange command, the RESET verification condition from the plurality ofstored RESET verification conditions comprises: selecting a first RESETverification condition in response to determining that the receivedconfiguration change command is a SLC mode to MLC mode typeconfiguration change command; and selecting a second RESET verificationcondition in response to determining that the received configurationchange command is a MLC mode to SLC mode type configuration changecommand.
 12. The method of claim 11, wherein: a first current value ofthe first RESET verification condition is a lower current value than asecond current value of the second RESET verification condition; or afirst voltage value of the first RESET verification condition is ahigher voltage value than a second voltage value of the second RESETverification condition.
 13. The method of claim 9, further comprising:in response to programming the PCRAM cell using the modified RESET pulseand successively until the PCRAM cell condition is determined meet theselected RESET verification condition: determining the PCRAM cellcondition; determining whether the determined PCRAM cell condition meetsthe selected RESET verification condition; modifying the modified RESETpulse to increase one or both of its current amplitude and its pulsewidth in response to determining the PCRAM cell condition does not meetthe selected RESET verification condition; and programming the PCRAMcell using the modified RESET pulse.
 14. The method of claim 9, furthercomprising, after determining the PCRAM cell condition meets theselected RESET verification condition: determining a RESET programcondition operation is to be performed for the PCRAM cell; determiningwhether the PCRAM cell is in a SLC mode or a MLC mode in response todetermining the RESET program condition operation is to be performed forthe PCRAM cell; in response to determining that the PCRAM cell is in theMLC mode: selecting a first RESET program condition; and programming thePCRAM cell to an intermediate state associated with the RESET programcondition operation using incremental step pulse programming initiatedat the first RESET program condition; and in response to determiningthat the PCRAM cell is in the SLC mode: selecting a second RESET programcondition; and programming the PCRAM cell to a high resistance state(HRS) using the second RESET program condition.
 15. The method of claim14, wherein: the first RESET program condition is configured to generatea first waveform having a first current amplitude and a first pulsewidth; the second RESET program condition is configured to generate asecond waveform having a second current amplitude and a second pulsewidth; and the first current amplitude has a higher current value thanthe second current amplitude and the first pulse width has a longer timeduration than the second pulse width.
 16. A method for configuring aphase-change random-access memory (PCRAM) cell, comprising: determininga RESET program condition operation is to be performed for the PCRAMcell; determining whether the PCRAM cell is in a single-level-cell (SLC)mode or a multi-level-cell (MLC) mode in response to determining theRESET program condition operation is to be performed for the PCRAM cell;selecting a RESET program condition from a plurality of stored RESETprogram conditions based at least in part on whether the PCRAM cell isin the SLC mode or the MLC mode; and programming the PCRAM cell usingthe selected RESET program condition.
 17. The method of claim 16,wherein the plurality of stored RESET program conditions comprises: afirst RESET program condition configured to generate a first waveformhaving a first current amplitude and a first pulse width; and a secondRESET program condition configured to generate a second waveform havinga second current amplitude and a second pulse width.
 18. The method ofclaim 17, wherein: selecting the RESET program condition from theplurality of stored RESET program conditions based at least in part onwhether the PCRAM cell is in the SLC mode or the MLC mode comprises:selecting the second RESET program condition in response to determiningthat the PCRAM cell is in the SLC mode; and selecting the first RESETprogram condition in response to determining that the PCRAM cell is inthe MLC mode.
 19. The method of claim 18, wherein programming the PCRAMcell using the selected RESET program condition comprises: in responseto determining that the PCRAM cell is in the SLC mode, programming thePCRAM cell to a high resistance state (HRS) using the second RESETprogram condition; and in response to determining that the PCRAM cell isin the MLC mode, programming the PCRAM cell to an intermediate stateassociated with the RESET program condition operation using incrementalstep pulse programming initiated at the first RESET program condition.20. The method of claim 19, wherein the first current amplitude has ahigher current value than the second current amplitude and the firstpulse width has a longer time duration than the second pulse width.